diff --git a/.eslintrc.js b/.eslintrc.js
index 152622784940..7223f8117ea1 100644
--- a/.eslintrc.js
+++ b/.eslintrc.js
@@ -16,53 +16,23 @@ module.exports = {
     'no-console': OFF,
     // require radix argument in parseInt
     radix: ERROR,
+    'class-methods-use-this': OFF,
+    'react/no-multi-comp': OFF,
+    'import/no-extraneous-dependencies': OFF,
+    'react/no-danger': OFF,
+    'no-empty': [ERROR, {allowEmptyCatch: true}],
+
     // Existing ESLint errors sorted by frequency, silencing first.
     'react/button-has-type': OFF, // 1
-    null: OFF, // 1
-    'react/no-unused-state': OFF, // 1
-    'vars-on-top': OFF, // 1
     'react/forbid-prop-types': OFF, // 1
     'react/require-default-props': OFF, // 1
-    'lines-between-class-members': OFF, // 1
-    strict: OFF, // 1
-    'no-restricted-syntax': OFF, // 1
-    'no-path-concat': OFF, // 2
-    'one-var': OFF, // 2
-    'no-unused-expressions': OFF, // 2
-    'react/jsx-boolean-value': OFF, // 2
-    'jsx-a11y/html-has-lang': OFF, // 2
-    'no-var': OFF, // 2
-    'no-useless-return': OFF, // 2
-    'jsx-a11y/anchor-has-content': OFF, // 2
-    'react/jsx-no-comment-textnodes': OFF, // 3
-    'no-continue': OFF, // 3
-    'jsx-a11y/alt-text': OFF, // 3
-    'react/jsx-tag-spacing': OFF, // 3
-    'no-lonely-if': OFF, // 3
-    'react/sort-comp': OFF, // 4
-    'no-cond-assign': OFF, // 4
-    'no-use-before-define': OFF, // 4
-    'no-empty': OFF, // 4
-    'no-shadow': OFF, // 4
-    'class-methods-use-this': OFF, // 5
-    eqeqeq: OFF, // 5
-    'react/no-multi-comp': OFF, // 5
-    'react/no-array-index-key': OFF, // 6
-    'no-underscore-dangle': OFF, // 6
-    'array-callback-return': OFF, // 6
-    'import/no-extraneous-dependencies': OFF, // 7
-    'no-else-return': OFF, // 9
     'jsx-a11y/anchor-is-valid': OFF, // 9
-    'import/order': OFF, // 10
     'arrow-body-style': OFF, // 10
-    camelcase: OFF, // 10
     'react/jsx-curly-brace-presence': OFF, // 11
     'react/no-unescaped-entities': OFF, // 12
     'no-param-reassign': OFF, // 12
-    'no-unused-vars': OFF, // 13
     'spaced-comment': OFF, // 14
     'import/no-unresolved': OFF, // 15
-    'react/no-danger': OFF, // 16
     'object-shorthand': OFF, // 16
     'dot-notation': OFF, // 19
     'react/prefer-stateless-function': OFF, // 22
diff --git a/examples/basics/core/Footer.js b/examples/basics/core/Footer.js
index 22d90f1492ef..41fbc0ff6f78 100644
--- a/examples/basics/core/Footer.js
+++ b/examples/basics/core/Footer.js
@@ -72,7 +72,7 @@ class Footer extends React.Component {
               href={this.props.config.repoUrl}
               data-icon="octicon-star"
               data-count-href="/facebook/docusaurus/stargazers"
-              data-show-count={true}
+              data-show-count="true"
               data-count-aria-label="# stargazers on GitHub"
               aria-label="Star this project on GitHub">
               Star
diff --git a/examples/basics/pages/en/index.js b/examples/basics/pages/en/index.js
index d6db81ee8f65..0afae4234ebe 100755
--- a/examples/basics/pages/en/index.js
+++ b/examples/basics/pages/en/index.js
@@ -52,11 +52,11 @@ const SplashContainer = props => (
 
 const Logo = props => (
   <div className="projectLogo">
-    <img src={props.img_src} />
+    <img src={props.img_src} alt="Project Logo" />
   </div>
 );
 
-const ProjectTitle = props => (
+const ProjectTitle = () => (
   <h2 className="projectTitle">
     {siteConfig.title}
     <small>{siteConfig.tagline}</small>
@@ -99,7 +99,7 @@ const Block = props => (
   </Container>
 );
 
-const Features = props => (
+const Features = () => (
   <Block layout="fourColumn">
     {[
       {
@@ -118,7 +118,7 @@ const Features = props => (
   </Block>
 );
 
-const FeatureCallout = props => (
+const FeatureCallout = () => (
   <div
     className="productShowcaseSection paddingBottom"
     style={{textAlign: 'center'}}>
@@ -127,7 +127,7 @@ const FeatureCallout = props => (
   </div>
 );
 
-const LearnHow = props => (
+const LearnHow = () => (
   <Block background="light">
     {[
       {
@@ -140,7 +140,7 @@ const LearnHow = props => (
   </Block>
 );
 
-const TryOut = props => (
+const TryOut = () => (
   <Block id="try">
     {[
       {
@@ -153,7 +153,7 @@ const TryOut = props => (
   </Block>
 );
 
-const Description = props => (
+const Description = () => (
   <Block background="dark">
     {[
       {
@@ -170,21 +170,16 @@ const Showcase = props => {
   if ((siteConfig.users || []).length === 0) {
     return null;
   }
-  const showcase = siteConfig.users
-    .filter(user => {
-      return user.pinned;
-    })
-    .map((user, i) => {
-      return (
-        <a href={user.infoLink} key={i}>
-          <img src={user.image} alt={user.caption} title={user.caption} />
-        </a>
-      );
-    });
+
+  const showcase = siteConfig.users.filter(user => user.pinned).map(user => (
+    <a href={user.infoLink} key={user.infoLink}>
+      <img src={user.image} alt={user.caption} title={user.caption} />
+    </a>
+  ));
 
   return (
     <div className="productShowcaseSection paddingBottom">
-      <h2>{"Who's Using This?"}</h2>
+      <h2>Who's Using This?</h2>
       <p>This project is used by all these people</p>
       <div className="logos">{showcase}</div>
       <div className="more-users">
diff --git a/examples/basics/pages/en/users.js b/examples/basics/pages/en/users.js
index c113bf5c7264..458eb9757094 100644
--- a/examples/basics/pages/en/users.js
+++ b/examples/basics/pages/en/users.js
@@ -17,14 +17,13 @@ class Users extends React.Component {
     if ((siteConfig.users || []).length === 0) {
       return null;
     }
+
     const editUrl = siteConfig.repoUrl + '/edit/master/website/siteConfig.js';
-    const showcase = siteConfig.users.map((user, i) => {
-      return (
-        <a href={user.infoLink} key={i}>
-          <img src={user.image} alt={user.caption} title={user.caption} />
-        </a>
-      );
-    });
+    const showcase = siteConfig.users.map(user => (
+      <a href={user.infoLink} key={user.infoLink}>
+        <img src={user.image} alt={user.caption} title={user.caption} />
+      </a>
+    ));
 
     return (
       <div className="mainContainer">
diff --git a/lib/__tests__/build-files.test.js b/lib/__tests__/build-files.test.js
index 9a0048359b8b..7651848fe561 100644
--- a/lib/__tests__/build-files.test.js
+++ b/lib/__tests__/build-files.test.js
@@ -52,7 +52,6 @@ beforeAll(() => {
       inputAssetsFiles,
       outputAssetsFiles,
     ] = results;
-    return;
   });
 });
 
diff --git a/lib/core/BlogPageLayout.js b/lib/core/BlogPageLayout.js
index 588bf0c6d609..6c1d07d179b7 100644
--- a/lib/core/BlogPageLayout.js
+++ b/lib/core/BlogPageLayout.js
@@ -5,11 +5,11 @@
  * LICENSE file in the root directory of this source tree.
  */
 
+const React = require('react');
 const BlogPost = require('./BlogPost.js');
 const BlogSidebar = require('./BlogSidebar.js');
 const Container = require('./Container.js');
 const MetadataBlog = require('./MetadataBlog.js');
-const React = require('react');
 const Site = require('./Site.js');
 const utils = require('./utils.js');
 
@@ -46,7 +46,7 @@ class BlogPageLayout extends React.Component {
                     <BlogPost
                       post={post}
                       content={post.content}
-                      truncate={true}
+                      truncate
                       key={
                         utils.getPath(post.path, this.props.config.cleanUrl) +
                         post.title
diff --git a/lib/core/BlogPost.js b/lib/core/BlogPost.js
index 2ced66df9b2b..a75e4bc5e0a1 100644
--- a/lib/core/BlogPost.js
+++ b/lib/core/BlogPost.js
@@ -5,9 +5,9 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-const MarkdownBlock = require('./MarkdownBlock.js');
 const React = require('react');
 
+const MarkdownBlock = require('./MarkdownBlock.js');
 const utils = require('./utils.js');
 
 // inner blog component for the article itself, without sidebar/header/footer
@@ -46,32 +46,21 @@ class BlogPost extends React.Component {
     const className =
       'authorPhoto' +
       (post.author && post.authorTitle ? ' authorPhotoBig' : '');
-    if (post.authorFBID) {
-      return (
-        <div className={className}>
-          <a href={post.authorURL} target="_blank" rel="noreferrer noopener">
-            <img
-              src={
-                'https://graph.facebook.com/' +
-                post.authorFBID +
-                '/picture/?height=200&width=200'
-              }
-              alt={post.author}
-            />
-          </a>
-        </div>
-      );
-    } else if (post.authorImageURL) {
+    if (post.authorFBID || post.authorImageURL) {
+      const authorImageURL = post.authorFBID
+        ? `https://graph.facebook.com/${
+            post.authorFBID
+          }/picture/?height=200&width=200`
+        : post.authorImageURL;
       return (
         <div className={className}>
           <a href={post.authorURL} target="_blank" rel="noreferrer noopener">
-            <img src={post.authorImageURL} />
+            <img src={authorImageURL} alt={post.author} />
           </a>
         </div>
       );
-    } else {
-      return null;
     }
+    return null;
   }
 
   renderTitle() {
diff --git a/lib/core/BlogPostLayout.js b/lib/core/BlogPostLayout.js
index 799ae3e60253..aa58b55b9a58 100644
--- a/lib/core/BlogPostLayout.js
+++ b/lib/core/BlogPostLayout.js
@@ -5,19 +5,31 @@
  * LICENSE file in the root directory of this source tree.
  */
 
+const classNames = require('classnames');
 const React = require('react');
+
 const BlogPost = require('./BlogPost.js');
 const BlogSidebar = require('./BlogSidebar.js');
 const Container = require('./Container.js');
 const Site = require('./Site.js');
 const OnPageNav = require('./nav/OnPageNav.js');
 const utils = require('./utils.js');
-const classNames = require('classnames');
 
 // used for entire blog posts, i.e., each written blog article with sidebar with site header/footer
 class BlogPostLayout extends React.Component {
+  getDescription() {
+    const descLines = this.props.children.trim().split('\n');
+    for (let i = 0; i < descLines.length; i++) {
+      // Don't want blank lines or descriptions that are raw image rendering strings.
+      if (descLines[i] && !descLines[i].startsWith('![')) {
+        return descLines[i];
+      }
+    }
+    return null;
+  }
+
   renderSocialButtons() {
-    let post = this.props.metadata;
+    const post = this.props.metadata;
     post.path = utils.getPath(post.path, this.props.config.cleanUrl);
 
     const fbComment = this.props.config.facebookAppId &&
@@ -72,8 +84,9 @@ class BlogPostLayout extends React.Component {
           }
           data-related={this.props.config.twitter}
           data-via={post.authorTwitter}
-          data-show-count="false"
-        />
+          data-show-count="false">
+          Tweet
+        </a>
       </div>
     );
 
@@ -86,17 +99,6 @@ class BlogPostLayout extends React.Component {
     );
   }
 
-  getDescription() {
-    const descLines = this.props.children.trim().split('\n');
-    for (var i = 0; i < descLines.length; i++) {
-      // Don't want blank lines or descriptions that are raw image rendering strings
-      if (descLines[i] && !descLines[i].startsWith('![')) {
-        return descLines[i];
-      }
-    }
-    return null;
-  }
-
   render() {
     const hasOnPageNav = this.props.config.onPageNav === 'separate';
     const post = this.props.metadata;
diff --git a/lib/core/BlogSidebar.js b/lib/core/BlogSidebar.js
index 5cdd2f1afea1..c730b14128ce 100644
--- a/lib/core/BlogSidebar.js
+++ b/lib/core/BlogSidebar.js
@@ -17,7 +17,7 @@ class BlogSidebar extends React.Component {
     let blogSidebarTitleConfig = this.props.config.blogSidebarTitle || {};
     let blogSidebarTitle = blogSidebarTitleConfig.default || 'Recent Posts';
     if (this.props.config.blogSidebarCount) {
-      if (this.props.config.blogSidebarCount == 'ALL') {
+      if (this.props.config.blogSidebarCount === 'ALL') {
         blogSidebarCount = MetadataBlog.length;
         blogSidebarTitle = blogSidebarTitleConfig.all || 'All Blog Posts';
       } else {
diff --git a/lib/core/Doc.js b/lib/core/Doc.js
index 941078f88cd4..a9b0c7ee58cc 100644
--- a/lib/core/Doc.js
+++ b/lib/core/Doc.js
@@ -43,7 +43,7 @@ class Doc extends React.Component {
     // If internationalization is enabled, show Recruiting link instead of Edit Link.
     if (
       this.props.language &&
-      this.props.language != 'en' &&
+      this.props.language !== 'en' &&
       this.props.config.translationRecruitingLink
     ) {
       editLink = (
diff --git a/lib/core/DocsLayout.js b/lib/core/DocsLayout.js
index d75336f01682..89b47198c04c 100644
--- a/lib/core/DocsLayout.js
+++ b/lib/core/DocsLayout.js
@@ -5,16 +5,17 @@
  * LICENSE file in the root directory of this source tree.
  */
 
+const classNames = require('classnames');
+const path = require('path');
 const React = require('react');
+const url = require('url');
+
 const Container = require('./Container.js');
 const Doc = require('./Doc.js');
 const DocsSidebar = require('./DocsSidebar.js');
 const OnPageNav = require('./nav/OnPageNav.js');
 const Site = require('./Site.js');
 const translation = require('../server/translation.js');
-const classNames = require('classnames');
-const path = require('path');
-const url = require('url');
 
 // component used to generate whole webpage for docs, including sidebar/header/footer
 class DocsLayout extends React.Component {
diff --git a/lib/core/GridBlock.js b/lib/core/GridBlock.js
index 8d728dd9c302..612dd90a15bf 100755
--- a/lib/core/GridBlock.js
+++ b/lib/core/GridBlock.js
@@ -48,37 +48,33 @@ class GridBlock extends React.Component {
   }
 
   renderBlockImage(image, imageLink, imageAlt) {
-    if (image) {
-      if (imageLink) {
-        return (
-          <div className="blockImage">
-            <a href={imageLink}>
-              <img src={image} alt={imageAlt} />
-            </a>
-          </div>
-        );
-      } else {
-        return (
-          <div className="blockImage">
-            <img src={image} alt={imageAlt} />
-          </div>
-        );
-      }
-    } else {
+    if (!image) {
       return null;
     }
+
+    return (
+      <div className="blockImage">
+        {imageLink ? (
+          <a href={imageLink}>
+            <img src={image} alt={imageAlt} />
+          </a>
+        ) : (
+          <img src={image} alt={imageAlt} />
+        )}
+      </div>
+    );
   }
 
   renderBlockTitle(title) {
-    if (title) {
-      return (
-        <h2>
-          <MarkdownBlock>{title}</MarkdownBlock>
-        </h2>
-      );
-    } else {
+    if (!title) {
       return null;
     }
+
+    return (
+      <h2>
+        <MarkdownBlock>{title}</MarkdownBlock>
+      </h2>
+    );
   }
 
   render() {
diff --git a/lib/core/Head.js b/lib/core/Head.js
index 7d61786f50be..e8bfaad84225 100644
--- a/lib/core/Head.js
+++ b/lib/core/Head.js
@@ -11,10 +11,7 @@ const React = require('react');
 class Head extends React.Component {
   render() {
     const links = this.props.config.headerLinks;
-    let hasBlog = false;
-    links.map(link => {
-      if (link.blog) hasBlog = true;
-    });
+    const hasBlog = links.some(link => link.blog);
 
     let highlight = {
       version: '9.12.0',
@@ -137,21 +134,13 @@ class Head extends React.Component {
 
         {/* External resources */}
         {this.props.config.stylesheets &&
-          this.props.config.stylesheets.map(function(source, idx) {
-            return (
-              <link rel="stylesheet" key={'stylesheet' + idx} href={source} />
-            );
-          })}
+          this.props.config.stylesheets.map(source => (
+            <link rel="stylesheet" key={source} href={source} />
+          ))}
         {this.props.config.scripts &&
-          this.props.config.scripts.map(function(source, idx) {
-            return (
-              <script
-                type="text/javascript"
-                key={'script' + idx}
-                src={source}
-              />
-            );
-          })}
+          this.props.config.scripts.map(source => (
+            <script type="text/javascript" key={source} src={source} />
+          ))}
 
         {this.props.config.scrollToTop && (
           <script
diff --git a/lib/core/Header.js b/lib/core/Header.js
deleted file mode 100644
index 3287fd3fd4f4..000000000000
--- a/lib/core/Header.js
+++ /dev/null
@@ -1,28 +0,0 @@
-/**
- * Copyright (c) 2017-present, Facebook, Inc.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- */
-
-const React = require('react');
-const toSlug = require('./toSlug.js');
-
-class Header extends React.Component {
-  render() {
-    const slug = toSlug(this.props.toSlug || this.props.children);
-    const Heading = 'h' + this.props.level;
-
-    return (
-      <Heading {...this.props}>
-        <a className="anchor" id={slug} />
-        {this.props.children}{' '}
-        <a className="hash-link" href={'#' + slug}>
-          #
-        </a>
-      </Heading>
-    );
-  }
-}
-
-module.exports = Header;
diff --git a/lib/core/Redirect.js b/lib/core/Redirect.js
index 20705c3654ff..a719ee532a5b 100644
--- a/lib/core/Redirect.js
+++ b/lib/core/Redirect.js
@@ -29,7 +29,7 @@ class Redirect extends React.Component {
     const redirect = this.props.redirect || false;
 
     return (
-      <html>
+      <html lang="en">
         <Head
           config={this.props.config}
           description={description}
diff --git a/lib/core/Remarkable.js b/lib/core/Remarkable.js
index 7a2587bafe37..d632819820cc 100644
--- a/lib/core/Remarkable.js
+++ b/lib/core/Remarkable.js
@@ -5,8 +5,6 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-'use strict';
-
 const React = require('react');
 const renderMarkdown = require('./renderMarkdown.js');
 
@@ -20,22 +18,21 @@ class Remarkable extends React.Component {
           }}
         />
       );
-    } else {
-      return React.Children.map(this.props.children, child => {
-        if (typeof child === 'string') {
-          return (
-            <span dangerouslySetInnerHTML={{__html: renderMarkdown(child)}} />
-          );
-        } else {
-          return child;
-        }
-      });
     }
+
+    return React.Children.map(this.props.children, child => {
+      if (typeof child === 'string') {
+        return (
+          <span dangerouslySetInnerHTML={{__html: renderMarkdown(child)}} />
+        );
+      }
+
+      return child;
+    });
   }
 
   render() {
-    var Container = this.props.container;
-
+    const Container = this.props.container;
     return <Container>{this.content()}</Container>;
   }
 }
diff --git a/lib/core/Site.js b/lib/core/Site.js
index c27c2e95a288..45b58aa0f14e 100644
--- a/lib/core/Site.js
+++ b/lib/core/Site.js
@@ -39,14 +39,8 @@ class Site extends React.Component {
       docsVersion = latestVersion;
     }
 
-    // We do not want a lang attribute for the html tag if we don't have a language set
-    const htmlElementProps = {};
-    if (this.props.language) {
-      htmlElementProps.lang = this.props.language;
-    }
-
     return (
-      <html {...htmlElementProps}>
+      <html lang={this.props.language}>
         <Head
           config={this.props.config}
           description={description}
diff --git a/lib/core/__tests__/anchors.test.js b/lib/core/__tests__/anchors.test.js
index 2ccd4312b53a..f78b2f139c66 100644
--- a/lib/core/__tests__/anchors.test.js
+++ b/lib/core/__tests__/anchors.test.js
@@ -5,8 +5,8 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-const anchors = require('../anchors');
 const rules = require('remarkable/lib/rules');
+const anchors = require('../anchors');
 
 const md = {
   renderer: {
diff --git a/lib/core/__tests__/getTOC.test.js b/lib/core/__tests__/getTOC.test.js
index 0826df93784f..0f329b8a36b9 100644
--- a/lib/core/__tests__/getTOC.test.js
+++ b/lib/core/__tests__/getTOC.test.js
@@ -11,7 +11,7 @@ const getTOC = require('../getTOC');
 
 const mdContents = readFileSync(
   path.join(__dirname, '__fixtures__', 'getTOC.md'),
-  'utf-8'
+  'utf8'
 );
 
 test('with defaults', () => {
diff --git a/lib/core/__tests__/utils.test.js b/lib/core/__tests__/utils.test.js
index 9a172d79567b..04ccef614e20 100644
--- a/lib/core/__tests__/utils.test.js
+++ b/lib/core/__tests__/utils.test.js
@@ -6,17 +6,17 @@
  */
 
 const path = require('path');
+const fs = require('fs');
 const utils = require('../utils');
-const readFileSync = require('fs').readFileSync;
 
-const blogPostWithTruncateContents = readFileSync(
+const blogPostWithTruncateContents = fs.readFileSync(
   path.join(__dirname, '__fixtures__', 'blog-post-with-truncate.md'),
-  'utf-8'
+  'utf8'
 );
 
-const blogPostWithoutTruncateContents = readFileSync(
+const blogPostWithoutTruncateContents = fs.readFileSync(
   path.join(__dirname, '__fixtures__', 'blog-post-without-truncate.md'),
-  'utf-8'
+  'utf8'
 );
 
 describe('utils', () => {
diff --git a/lib/core/getTOC.js b/lib/core/getTOC.js
index 45093c110b94..f1680469eded 100644
--- a/lib/core/getTOC.js
+++ b/lib/core/getTOC.js
@@ -52,8 +52,8 @@ module.exports = (content, headingTags = 'h2', subHeadingTags = 'h3') => {
     if (headingLevels.includes(heading.lvl)) {
       toc.push(entry);
       current = entry;
-    } else {
-      current && current.children.push(entry);
+    } else if (current) {
+      current.children.push(entry);
     }
   });
 
diff --git a/lib/core/nav/HeaderNav.js b/lib/core/nav/HeaderNav.js
index 2285ec3cf964..78790c2c1a39 100644
--- a/lib/core/nav/HeaderNav.js
+++ b/lib/core/nav/HeaderNav.js
@@ -89,6 +89,7 @@ class LanguageDropDown extends React.Component {
             <img
               className="languages-icon"
               src={this.props.baseUrl + 'img/language.svg'}
+              alt="Languages icon"
             />
             {currentLanguage}
           </a>
@@ -120,12 +121,6 @@ class LanguageDropDown extends React.Component {
 
 // header navbar used by all pages generated with docusaurus
 class HeaderNav extends React.Component {
-  constructor() {
-    super();
-    this.state = {
-      slideoutActive: false,
-    };
-  }
   // function to generate each header link, used with each object in siteConfig.headerLinks
   makeLinks(link) {
     let href;
@@ -143,7 +138,8 @@ class HeaderNav extends React.Component {
           />
         </li>
       );
-    } else if (link.languages) {
+    }
+    if (link.languages) {
       if (
         env.translation.enabled &&
         env.translation.enabledLanguages().length > 1
@@ -157,10 +153,10 @@ class HeaderNav extends React.Component {
             key="languagedropdown"
           />
         );
-      } else {
-        return null;
       }
-    } else if (link.doc) {
+      return null;
+    }
+    if (link.doc) {
       // set link to document with current page's language/version
       const langPart = env.translation.enabled
         ? (this.props.language || 'en') + '-'
@@ -238,47 +234,6 @@ class HeaderNav extends React.Component {
     );
   }
 
-  render() {
-    const headerClass = siteConfig.headerIcon
-      ? 'headerTitleWithLogo'
-      : 'headerTitle';
-    const versionsLink =
-      this.props.baseUrl +
-      (env.translation.enabled
-        ? this.props.language + '/versions' + extension
-        : 'versions' + extension);
-    return (
-      <div className="fixedHeaderContainer">
-        <div className="headerWrapper wrapper">
-          <header>
-            <a
-              href={
-                this.props.baseUrl +
-                (env.translation.enabled ? this.props.language : '')
-              }>
-              {siteConfig.headerIcon && (
-                <img
-                  className="logo"
-                  src={this.props.baseUrl + siteConfig.headerIcon}
-                  alt={siteConfig.title}
-                />
-              )}
-              {!this.props.config.disableHeaderTitle && (
-                <h2 className={headerClass}>{this.props.title}</h2>
-              )}
-            </a>
-            {env.versioning.enabled && (
-              <a href={versionsLink}>
-                <h3>{this.props.version || env.versioning.defaultVersion}</h3>
-              </a>
-            )}
-            {this.renderResponsiveNav()}
-          </header>
-        </div>
-      </div>
-    );
-  }
-
   renderResponsiveNav() {
     const headerLinks = this.props.config.headerLinks;
     // add language drop down to end if location not specified
@@ -336,6 +291,47 @@ class HeaderNav extends React.Component {
       </div>
     );
   }
+
+  render() {
+    const headerClass = siteConfig.headerIcon
+      ? 'headerTitleWithLogo'
+      : 'headerTitle';
+    const versionsLink =
+      this.props.baseUrl +
+      (env.translation.enabled
+        ? this.props.language + '/versions' + extension
+        : 'versions' + extension);
+    return (
+      <div className="fixedHeaderContainer">
+        <div className="headerWrapper wrapper">
+          <header>
+            <a
+              href={
+                this.props.baseUrl +
+                (env.translation.enabled ? this.props.language : '')
+              }>
+              {siteConfig.headerIcon && (
+                <img
+                  className="logo"
+                  src={this.props.baseUrl + siteConfig.headerIcon}
+                  alt={siteConfig.title}
+                />
+              )}
+              {!this.props.config.disableHeaderTitle && (
+                <h2 className={headerClass}>{this.props.title}</h2>
+              )}
+            </a>
+            {env.versioning.enabled && (
+              <a href={versionsLink}>
+                <h3>{this.props.version || env.versioning.defaultVersion}</h3>
+              </a>
+            )}
+            {this.renderResponsiveNav()}
+          </header>
+        </div>
+      </div>
+    );
+  }
 }
 
 HeaderNav.defaultProps = {
diff --git a/lib/core/nav/OnPageNav.js b/lib/core/nav/OnPageNav.js
index ce20582b12a4..2690f9564919 100644
--- a/lib/core/nav/OnPageNav.js
+++ b/lib/core/nav/OnPageNav.js
@@ -23,8 +23,8 @@ const Headings = ({headings}) => {
   if (!headings.length) return null;
   return (
     <ul className="toc-headings">
-      {headings.map((heading, i) => (
-        <li key={i}>
+      {headings.map(heading => (
+        <li key={heading.hashLink}>
           <Link hashLink={heading.hashLink} content={heading.content} />
           <Headings headings={heading.children} />
         </li>
diff --git a/lib/core/nav/SideNav.js b/lib/core/nav/SideNav.js
index a915ed86d0e8..fd3da91229f1 100644
--- a/lib/core/nav/SideNav.js
+++ b/lib/core/nav/SideNav.js
@@ -13,75 +13,6 @@ const translation = require('../../server/translation.js');
 const utils = require('../utils.js');
 
 class SideNav extends React.Component {
-  render() {
-    return (
-      <nav className="toc">
-        <div className="toggleNav">
-          <section className="navWrapper wrapper">
-            <div className="navBreadcrumb wrapper">
-              <div className="navToggle" id="navToggler">
-                <i />
-              </div>
-              <h2>
-                <i>›</i>
-                <span>
-                  {this.getLocalizedCategoryString(this.props.current.category)}
-                </span>
-              </h2>
-              {siteConfig.onPageNav === 'separate' && (
-                <div className="tocToggler" id="tocToggler">
-                  <i className="icon-toc" />
-                </div>
-              )}
-            </div>
-            <div className="navGroups">
-              {this.props.contents.map(this.renderCategory, this)}
-            </div>
-          </section>
-        </div>
-        <script
-          dangerouslySetInnerHTML={{
-            __html: `
-            document.addEventListener('DOMContentLoaded', function() {
-              createToggler('#navToggler', '#docsNav', 'docsSliderActive');
-              createToggler('#tocToggler', 'body', 'tocActive');
-
-              const headings = document.querySelector('.toc-headings');
-              headings && headings.addEventListener('click', function(event) {
-                if (event.target.tagName === 'A') {
-                  document.body.classList.remove('tocActive');
-                }
-              }, false);
-
-              function createToggler(togglerSelector, targetSelector, className) {
-                var toggler = document.querySelector(togglerSelector);
-                var target = document.querySelector(targetSelector);
-
-                toggler.onclick = function(event) {
-                  event.preventDefault();
-
-                  target.classList.toggle(className);
-                };
-              }
-            });
-        `,
-          }}
-        />
-      </nav>
-    );
-  }
-
-  renderCategory(category) {
-    return (
-      <div className="navGroup" key={category.name}>
-        <h3 className="navGroupCategoryTitle">
-          {this.getLocalizedCategoryString(category.name)}
-        </h3>
-        <ul>{category.links.map(this.renderItemLink, this)}</ul>
-      </div>
-    );
-  }
-
   // return appropriately translated category string
   getLocalizedCategoryString(category) {
     let categoryString = translation[this.props.language]
@@ -129,6 +60,17 @@ class SideNav extends React.Component {
     return null;
   }
 
+  renderCategory(category) {
+    return (
+      <div className="navGroup" key={category.name}>
+        <h3 className="navGroupCategoryTitle">
+          {this.getLocalizedCategoryString(category.name)}
+        </h3>
+        <ul>{category.links.map(this.renderItemLink, this)}</ul>
+      </div>
+    );
+  }
+
   renderItemLink(link) {
     const itemClasses = classNames('navListItem', {
       navListItemActive: link.id === this.props.current.id,
@@ -141,6 +83,64 @@ class SideNav extends React.Component {
       </li>
     );
   }
+
+  render() {
+    return (
+      <nav className="toc">
+        <div className="toggleNav">
+          <section className="navWrapper wrapper">
+            <div className="navBreadcrumb wrapper">
+              <div className="navToggle" id="navToggler">
+                <i />
+              </div>
+              <h2>
+                <i>›</i>
+                <span>
+                  {this.getLocalizedCategoryString(this.props.current.category)}
+                </span>
+              </h2>
+              {siteConfig.onPageNav === 'separate' && (
+                <div className="tocToggler" id="tocToggler">
+                  <i className="icon-toc" />
+                </div>
+              )}
+            </div>
+            <div className="navGroups">
+              {this.props.contents.map(this.renderCategory, this)}
+            </div>
+          </section>
+        </div>
+        <script
+          dangerouslySetInnerHTML={{
+            __html: `
+            document.addEventListener('DOMContentLoaded', function() {
+              createToggler('#navToggler', '#docsNav', 'docsSliderActive');
+              createToggler('#tocToggler', 'body', 'tocActive');
+
+              const headings = document.querySelector('.toc-headings');
+              headings && headings.addEventListener('click', function(event) {
+                if (event.target.tagName === 'A') {
+                  document.body.classList.remove('tocActive');
+                }
+              }, false);
+
+              function createToggler(togglerSelector, targetSelector, className) {
+                var toggler = document.querySelector(togglerSelector);
+                var target = document.querySelector(targetSelector);
+
+                toggler.onclick = function(event) {
+                  event.preventDefault();
+
+                  target.classList.toggle(className);
+                };
+              }
+            });
+        `,
+          }}
+        />
+      </nav>
+    );
+  }
 }
 
 SideNav.defaultProps = {
diff --git a/lib/core/renderMarkdown.js b/lib/core/renderMarkdown.js
index 555dc503a565..cdac0be9b5cb 100644
--- a/lib/core/renderMarkdown.js
+++ b/lib/core/renderMarkdown.js
@@ -42,17 +42,23 @@ class MarkdownRenderer {
                 // every single language (https://github.com/PrismJS/prism/issues/593)
                 require('prismjs/components/prism-' + language + '.min');
                 return prismjs.highlight(str, prismjs.languages[language]);
-              } catch (err) {}
+              } catch (err) {
+                console.error(err);
+              }
             }
             if (hljs.getLanguage(lang)) {
               return hljs.highlight(lang, str).value;
             }
-          } catch (err) {}
+          } catch (err) {
+            console.error(err);
+          }
         }
 
         try {
           return hljs.highlightAuto(str).value;
-        } catch (err) {}
+        } catch (err) {
+          console.error(err);
+        }
 
         return '';
       },
@@ -70,11 +76,11 @@ class MarkdownRenderer {
       });
     }
 
-    this._md = md;
+    this.md = md;
   }
 
   toHtml(source) {
-    const html = this._md.render(source);
+    const html = this.md.render(source);
 
     // Ensure fenced code blocks use Highlight.js hljs class
     // https://github.com/jonschlinkert/remarkable/issues/224
diff --git a/lib/core/utils.js b/lib/core/utils.js
index 9f12ef3eb05d..ce8e6f4e5027 100644
--- a/lib/core/utils.js
+++ b/lib/core/utils.js
@@ -26,12 +26,11 @@ function removeExtension(path) {
 
 function getPath(path, cleanUrl = false) {
   if (cleanUrl) {
-    if (path.endsWith('/index.html')) {
-      return path.replace(/\/index.html$/, '');
-    } else {
-      return removeExtension(path);
-    }
+    return path.endsWith('/index.html')
+      ? path.replace(/\/index.html$/, '')
+      : removeExtension(path);
   }
+
   return path;
 }
 
diff --git a/lib/publish-gh-pages.js b/lib/publish-gh-pages.js
index 44131b13840d..6460a3fd755c 100755
--- a/lib/publish-gh-pages.js
+++ b/lib/publish-gh-pages.js
@@ -111,16 +111,14 @@ if (defaultBranch !== DEPLOYMENT_BRANCH) {
       shell.echo(`Error: Git checkout ${DEPLOYMENT_BRANCH} failed`);
       shell.exit(1);
     }
-  } else {
-    if (
-      shell.exec(`git checkout -b ${DEPLOYMENT_BRANCH}`).code +
-        shell.exec(`git branch --set-upstream-to=origin/${DEPLOYMENT_BRANCH}`)
-          .code !==
-      0
-    ) {
-      shell.echo(`Error: Git checkout ${DEPLOYMENT_BRANCH} failed`);
-      shell.exit(1);
-    }
+  } else if (
+    shell.exec(`git checkout -b ${DEPLOYMENT_BRANCH}`).code +
+      shell.exec(`git branch --set-upstream-to=origin/${DEPLOYMENT_BRANCH}`)
+        .code !==
+    0
+  ) {
+    shell.echo(`Error: Git checkout ${DEPLOYMENT_BRANCH} failed`);
+    shell.exit(1);
   }
 }
 
@@ -140,7 +138,7 @@ const excludePath = `${PROJECT_NAME}-${DEPLOYMENT_BRANCH}`;
 fs.copy(
   fromPath,
   toPath,
-  (src, dest) => {
+  src => {
     if (src.indexOf('.DS_Store') !== -1) {
       return false;
     }
diff --git a/lib/rename-version.js b/lib/rename-version.js
index 7a4783d1cd18..c9d0231c139b 100755
--- a/lib/rename-version.js
+++ b/lib/rename-version.js
@@ -8,18 +8,16 @@
  */
 
 const chalk = require('chalk');
+const program = require('commander');
+const escapeStringRegexp = require('escape-string-regexp');
 const fs = require('fs');
 const glob = require('glob');
 const path = require('path');
+
 const metadataUtils = require('./server/metadataUtils.js');
 
 const CWD = process.cwd();
 
-// escape appropriate characters in a string to be used in a regex
-RegExp.escape = function(s) {
-  return s.replace(/[-/\\^$*+?.()|[\]{}]/g, '\\$&');
-};
-
 // generate a doc header from metadata
 function makeHeader(metadata) {
   let header = '---\n';
@@ -30,9 +28,8 @@ function makeHeader(metadata) {
   return header;
 }
 
-let currentVersion, newVersion;
-
-const program = require('commander');
+let currentVersion;
+let newVersion;
 
 program
   .arguments('<version_name> <new_version_name>')
@@ -123,7 +120,7 @@ if (fs.existsSync(currentSidebarFile)) {
   fs.renameSync(currentSidebarFile, newSidebarFile);
   let sidebarContent = fs.readFileSync(newSidebarFile, 'utf8');
   sidebarContent = sidebarContent.replace(
-    new RegExp(`version-${RegExp.escape(currentVersion)}-`, 'g'),
+    new RegExp(`version-${escapeStringRegexp(currentVersion)}-`, 'g'),
     `version-${newVersion}-`
   );
   fs.writeFileSync(newSidebarFile, sidebarContent);
diff --git a/lib/server/env.js b/lib/server/env.js
index 770d78ed2e11..fa7fc1dea1c5 100644
--- a/lib/server/env.js
+++ b/lib/server/env.js
@@ -13,9 +13,9 @@ const siteConfig = require(CWD + '/siteConfig.js');
 
 const join = path.join;
 
-const languages_js = join(CWD, 'languages.js');
-const versions_json = join(CWD, 'versions.json');
-const versions_js = join(CWD, 'pages/en/versions.js');
+const languagesFile = join(CWD, 'languages.js');
+const versionsJSONFile = join(CWD, 'versions.json');
+const versionsFile = join(CWD, 'pages/en/versions.js');
 
 class Translation {
   constructor() {
@@ -28,17 +28,15 @@ class Translation {
       },
     ];
 
-    this._load();
+    this.load();
   }
 
-  enabledLanguages() {
-    return this.languages.filter(lang => lang.enabled);
-  }
+  enabledLanguages = () => this.languages.filter(lang => lang.enabled);
 
-  _load() {
-    if (fs.existsSync(languages_js)) {
+  load() {
+    if (fs.existsSync(languagesFile)) {
       this.enabled = true;
-      this.languages = require(languages_js);
+      this.languages = require(languagesFile);
     }
   }
 }
@@ -50,7 +48,7 @@ class Versioning {
     this.versions = [];
     this.missingVersionsPage = false;
 
-    this._load();
+    this.load();
   }
 
   printMissingVersionsPageError() {
@@ -61,16 +59,16 @@ class Versioning {
     );
   }
 
-  _load() {
-    if (fs.existsSync(versions_json)) {
+  load() {
+    if (fs.existsSync(versionsJSONFile)) {
       this.enabled = true;
-      this.versions = JSON.parse(fs.readFileSync(versions_json, 'utf8'));
+      this.versions = JSON.parse(fs.readFileSync(versionsJSONFile, 'utf8'));
       this.defaultVersion = siteConfig.defaultVersionShown
         ? siteConfig.defaultVersionShown
         : this.versions[0]; // otherwise show the latest version (other than next/master)
     }
 
-    if (!fs.existsSync(versions_js)) {
+    if (!fs.existsSync(versionsFile)) {
       this.missingVersionsPage = true;
     }
   }
diff --git a/lib/server/generate.js b/lib/server/generate.js
index 1d4758f8a2fe..d0c76139c729 100644
--- a/lib/server/generate.js
+++ b/lib/server/generate.js
@@ -137,12 +137,10 @@ async function execute() {
       } else {
         file = join(CWD, 'versioned_docs', metadata.source);
       }
+    } else if (metadata.language === 'en') {
+      file = join(CWD, '..', readMetadata.getDocsPath(), metadata.source);
     } else {
-      if (metadata.language === 'en') {
-        file = join(CWD, '..', readMetadata.getDocsPath(), metadata.source);
-      } else {
-        file = join(CWD, 'translated_docs', metadata.language, metadata.source);
-      }
+      file = join(CWD, 'translated_docs', metadata.language, metadata.source);
     }
 
     if (!fs.existsSync(file)) {
@@ -156,14 +154,14 @@ async function execute() {
     const language = metadata.language;
 
     // generate table of contents if appropriate
-    if (rawContent && rawContent.indexOf(TABLE_OF_CONTENTS_TOKEN) != -1) {
+    if (rawContent && rawContent.indexOf(TABLE_OF_CONTENTS_TOKEN) !== -1) {
       rawContent = insertTableOfContents(rawContent);
     }
 
     let defaultVersion = env.versioning.defaultVersion;
 
     // replace any links to markdown files to their website html links
-    Object.keys(mdToHtml).forEach(function(key, index) {
+    Object.keys(mdToHtml).forEach(key => {
       let link = mdToHtml[key];
       link = utils.getPath(link, siteConfig.cleanUrl);
       link = link.replace('/en/', '/' + language + '/');
@@ -489,34 +487,33 @@ async function execute() {
       const match = regexLang.exec(normalizedFile);
       const langParts = match[1].split(sep);
       if (langParts.indexOf('en') !== -1) {
-        // copy and compile a page for each enabled language from the English file
+        // Copy and compile a page for each enabled language from the English file.
         for (let i = 0; i < enabledLanguages.length; i++) {
-          let language = enabledLanguages[i];
-          // skip conversion from english file if a file exists for this language
+          const language = enabledLanguages[i];
+          // Skip conversion from English file if a file exists for this language.
           if (
-            language !== 'en' &&
-            fs.existsSync(
+            language === 'en' ||
+            !fs.existsSync(
               normalizedFile.replace(sep + 'en' + sep, sep + language + sep)
             )
           ) {
-            continue;
+            translate.setLanguage(language);
+            const str = renderToStaticMarkupWithDoctype(
+              <Site
+                language={language}
+                config={siteConfig}
+                title={ReactComp.title}
+                description={ReactComp.description}
+                metadata={{id: pageID}}>
+                <ReactComp language={language} />
+              </Site>
+            );
+            writeFileAndCreateFolder(
+              // TODO: use path functions
+              targetFile.replace(sep + 'en' + sep, sep + language + sep),
+              str
+            );
           }
-          translate.setLanguage(language);
-          const str = renderToStaticMarkupWithDoctype(
-            <Site
-              language={language}
-              config={siteConfig}
-              title={ReactComp.title}
-              description={ReactComp.description}
-              metadata={{id: pageID}}>
-              <ReactComp language={language} />
-            </Site>
-          );
-          writeFileAndCreateFolder(
-            // TODO: use path functions
-            targetFile.replace(sep + 'en' + sep, sep + language + sep),
-            str
-          );
         }
 
         // write to base level
diff --git a/lib/server/metadataUtils.js b/lib/server/metadataUtils.js
index 16f801f14ecc..694eae723ef8 100644
--- a/lib/server/metadataUtils.js
+++ b/lib/server/metadataUtils.js
@@ -55,7 +55,9 @@ function extractMetadata(content) {
       .trim();
     try {
       value = JSON.parse(value);
-    } catch (e) {}
+    } catch (err) {
+      // Ignore the error as it means it's not a JSON value.
+    }
     metadata[key] = value;
   }
   return {metadata, rawContent: both.content};
diff --git a/lib/server/readCategories.js b/lib/server/readCategories.js
index 75d130785725..ecabed649ca5 100644
--- a/lib/server/readCategories.js
+++ b/lib/server/readCategories.js
@@ -5,10 +5,11 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-const CWD = process.cwd();
+const fs = require('fs');
 
 const Metadata = require('../core/metadata.js');
-const fs = require('fs');
+
+const CWD = process.cwd();
 let languages;
 if (fs.existsSync(CWD + '/languages.js')) {
   languages = require(CWD + '/languages.js');
@@ -24,10 +25,9 @@ if (fs.existsSync(CWD + '/languages.js')) {
 
 // returns data broken up into categories for a sidebar
 function readCategories(sidebar) {
-  const enabledLanguages = [];
-  languages.filter(lang => lang.enabled).map(lang => {
-    enabledLanguages.push(lang.tag);
-  });
+  const enabledLanguages = languages
+    .filter(lang => lang.enabled)
+    .map(lang => lang.tag);
 
   const allCategories = {};
 
@@ -88,7 +88,9 @@ function readCategories(sidebar) {
     let i = 0;
     while (metadata && i++ < 1000) {
       if (!currentCategory || metadata.category !== currentCategory.name) {
-        currentCategory && categories.push(currentCategory);
+        if (currentCategory) {
+          categories.push(currentCategory);
+        }
         currentCategory = {
           name: metadata.category,
           links: [],
diff --git a/lib/server/readMetadata.js b/lib/server/readMetadata.js
index e2fa4f32a8ae..b6570c8f6a4f 100644
--- a/lib/server/readMetadata.js
+++ b/lib/server/readMetadata.js
@@ -66,7 +66,8 @@ function readSidebar() {
 
     for (let i = 0; i < ids.length; i++) {
       const id = ids[i];
-      let previous, next;
+      let previous;
+      let next;
       if (i > 0) previous = ids[i - 1];
       if (i < ids.length - 1) next = ids[i + 1];
       order[id] = {
@@ -86,13 +87,13 @@ function processMetadata(file, refDir) {
   const language = utils.getLanguage(file, refDir) || 'en';
 
   const metadata = {};
-  for (const fieldName of Object.keys(result.metadata)) {
+  Object.keys(result.metadata).forEach(fieldName => {
     if (SupportedHeaderFields.has(fieldName)) {
       metadata[fieldName] = result.metadata[fieldName];
     } else {
       console.warn(`Header field "${fieldName}" in ${file} is not supported.`);
     }
-  }
+  });
 
   const rawContent = result.rawContent;
 
@@ -193,10 +194,8 @@ function generateMetadataDocs() {
       // create a default list of documents for each enabled language based on docs in English
       // these will get replaced if/when the localized file is downloaded from crowdin
       enabledLanguages
-        .filter(currentLanguage => {
-          return currentLanguage != 'en';
-        })
-        .map(currentLanguage => {
+        .filter(currentLanguage => currentLanguage !== 'en')
+        .forEach(currentLanguage => {
           let baseMetadata = Object.assign({}, metadata);
           baseMetadata['id'] = baseMetadata['id']
             .toString()
@@ -291,7 +290,7 @@ function generateMetadataDocs() {
   });
 
   fs.writeFileSync(
-    __dirname + '/../core/metadata.js',
+    path.join(__dirname, '/../core/metadata.js'),
     '/**\n' +
     ' * @' +
     'generated\n' + // separate this out for Nuclide treating @generated as readonly
@@ -360,7 +359,7 @@ function generateMetadataBlog() {
   );
 
   fs.writeFileSync(
-    __dirname + '/../core/MetadataBlog.js',
+    path.join(__dirname, '/../core/MetadataBlog.js'),
     '/**\n' +
     ' * @' +
     'generated\n' + // separate this out for Nuclide treating @generated as readonly
diff --git a/lib/server/server.js b/lib/server/server.js
index 21d29b98f8f4..98854aa2ebf0 100644
--- a/lib/server/server.js
+++ b/lib/server/server.js
@@ -5,6 +5,8 @@
  * LICENSE file in the root directory of this source tree.
  */
 
+/* eslint-disable no-cond-assign */
+
 function execute(port, options) {
   const extractTranslations = require('../write-translations');
 
@@ -45,8 +47,18 @@ function execute(port, options) {
   const join = path.join;
   const sep = path.sep;
 
-  // remove a module and child modules from require cache, so server does not have
-  // to be restarted
+  function removeModulePathFromCache(moduleName) {
+    /* eslint-disable no-underscore-dangle */
+    Object.keys(module.constructor._pathCache).forEach(function(cacheKey) {
+      if (cacheKey.indexOf(moduleName) > 0) {
+        delete module.constructor._pathCache[cacheKey];
+      }
+    });
+    /* eslint-enable no-underscore-dangle */
+  }
+
+  // Remove a module and child modules from require cache, so server
+  // does not have to be restarted.
   function removeModuleAndChildrenFromCache(moduleName) {
     let mod = require.resolve(moduleName);
     if (mod && (mod = require.cache[mod])) {
@@ -59,14 +71,6 @@ function execute(port, options) {
     }
   }
 
-  function removeModulePathFromCache(moduleName) {
-    Object.keys(module.constructor._pathCache).forEach(function(cacheKey) {
-      if (cacheKey.indexOf(moduleName) > 0) {
-        delete module.constructor._pathCache[cacheKey];
-      }
-    });
-  }
-
   /****************************************************************************/
 
   let readMetadata = require('./readMetadata.js');
@@ -147,6 +151,36 @@ function execute(port, options) {
     });
   }
 
+  function startLiveReload() {
+    // Start LiveReload server.
+    process.env.NODE_ENV = 'development';
+    const server = tinylr();
+    server.listen(constants.LIVE_RELOAD_PORT, function() {
+      console.log(
+        'LiveReload server started on port %d',
+        constants.LIVE_RELOAD_PORT
+      );
+    });
+
+    // gaze watches some specified dirs and triggers a callback when they change.
+    gaze(
+      [
+        '../' + readMetadata.getDocsPath() + '/**/*', // docs
+        '**/*', // website
+        '!node_modules/**/*', // node_modules
+      ],
+      function() {
+        // Listen for all kinds of file changes - modified/added/deleted.
+        this.on('all', function() {
+          // Notify LiveReload clients that there's a change.
+          // Typically, LiveReload will only refresh the changed paths,
+          // so we use / here to force a full-page reload.
+          server.notifyClients(['/']);
+        });
+      }
+    );
+  }
+
   /****************************************************************************/
 
   reloadMetadata();
@@ -200,12 +234,10 @@ function execute(port, options) {
       } else {
         file = join(CWD, 'versioned_docs', metadata.source);
       }
+    } else if (!env.translation.enabled || metadata.language === 'en') {
+      file = join(CWD, '..', readMetadata.getDocsPath(), metadata.source);
     } else {
-      if (!env.translation.enabled || metadata.language === 'en') {
-        file = join(CWD, '..', readMetadata.getDocsPath(), metadata.source);
-      } else {
-        file = join(CWD, 'translated_docs', metadata.language, metadata.source);
-      }
+      file = join(CWD, 'translated_docs', metadata.language, metadata.source);
     }
 
     if (!fs.existsSync(file)) {
@@ -225,7 +257,7 @@ function execute(port, options) {
     let defaultVersion = env.versioning.defaultVersion;
 
     // replace any links to markdown files to their website html links
-    Object.keys(mdToHtml).forEach(function(key, index) {
+    Object.keys(mdToHtml).forEach(key => {
       let link = mdToHtml[key];
       link = utils.getPath(link, siteConfig.cleanUrl);
       link = link.replace('/en/', '/' + language + '/');
@@ -333,8 +365,8 @@ function execute(port, options) {
       );
       const str = renderToStaticMarkupWithDoctype(blogPageComp);
 
-      let path = (page > 0 ? 'page' + (page + 1) : '') + '/index.html';
-      blogPages[path] = str;
+      const pagePath = (page > 0 ? 'page' + (page + 1) : '') + '/index.html';
+      blogPages[pagePath] = str;
     }
 
     let parts = req.path.toString().split('blog/');
@@ -398,7 +430,7 @@ function execute(port, options) {
 
   // handle all other main pages
   app.get(pageRouting(siteConfig.baseUrl), (req, res, next) => {
-    // look for user provided html file first
+    // Look for user-provided HTML file first.
     let htmlFile = req.path.toString().replace(siteConfig.baseUrl, '');
     htmlFile = join(CWD, 'pages', htmlFile);
     if (
@@ -470,8 +502,8 @@ function execute(port, options) {
       fs.existsSync((userFile = englishFile))
     ) {
       // copy into docusaurus so require paths work
-      let parts = userFile.split('pages' + sep);
-      let tempFile = join(__dirname, '..', 'pages', parts[1]);
+      let userFileParts = userFile.split('pages' + sep);
+      let tempFile = join(__dirname, '..', 'pages', userFileParts[1]);
       tempFile = tempFile.replace(
         path.basename(file),
         'temp' + path.basename(file)
@@ -501,7 +533,6 @@ function execute(port, options) {
       res.send(str);
     } else {
       next();
-      return;
     }
   });
 
@@ -598,36 +629,6 @@ function execute(port, options) {
 
   if (options.watch) startLiveReload();
   app.listen(port);
-
-  function startLiveReload() {
-    // Start LiveReload server.
-    process.env.NODE_ENV = 'development';
-    const server = tinylr();
-    server.listen(constants.LIVE_RELOAD_PORT, function() {
-      console.log(
-        'LiveReload server started on port %d',
-        constants.LIVE_RELOAD_PORT
-      );
-    });
-
-    // gaze watches some specified dirs and triggers a callback when they change.
-    gaze(
-      [
-        '../' + readMetadata.getDocsPath() + '/**/*', // docs
-        '**/*', // website
-        '!node_modules/**/*', // node_modules
-      ],
-      function() {
-        // Listen for all kinds of file changes - modified/added/deleted.
-        this.on('all', function() {
-          // Notify LiveReload clients that there's a change.
-          // Typically, LiveReload will only refresh the changed paths,
-          // so we use / here to force a full-page reload.
-          server.notifyClients(['/']);
-        });
-      }
-    );
-  }
 }
 
 module.exports = execute;
diff --git a/lib/server/sitemap.js b/lib/server/sitemap.js
index 1f5447024c7d..9d1ce66be021 100644
--- a/lib/server/sitemap.js
+++ b/lib/server/sitemap.js
@@ -32,8 +32,6 @@ MetadataBlog = require('../core/MetadataBlog.js');
 module.exports = function(callback) {
   console.log('sitemap.js triggered...');
 
-  let urls = [];
-
   let files = glob.sync(CWD + '/pages/en/**/*.js');
 
   // English-only is the default.
@@ -48,25 +46,23 @@ module.exports = function(callback) {
   // If we have a languages.js file, get all the enabled languages in there
   if (fs.existsSync(CWD + '/languages.js')) {
     let languages = require(CWD + '/languages.js');
-    enabledLanguages = languages.filter(lang => {
-      return lang.enabled == true;
-    });
+    enabledLanguages = languages.filter(lang => lang.enabled);
   }
 
-  // create a url mapping to all the enabled languages files
-  files.map(file => {
+  // Create a url mapping to all the enabled languages files
+  const urls = files.map(file => {
     let url = file.split('/pages/en')[1];
     url = siteConfig.cleanUrl
       ? url.replace(/\.js$/, '')
       : url.replace(/\.js$/, '.html');
-    let links = enabledLanguages.map(lang => {
+    const links = enabledLanguages.map(lang => {
       let langUrl = lang.tag + url;
       return {lang: lang.tag, url: langUrl};
     });
-    urls.push({url, changefreq: 'weekly', priority: 0.5, links});
+    return {url, changefreq: 'weekly', priority: 0.5, links};
   });
 
-  MetadataBlog.map(blog => {
+  MetadataBlog.forEach(blog => {
     urls.push({
       url: '/blog/' + utils.getPath(blog.path, siteConfig.cleanUrl),
       changefreq: 'weekly',
@@ -76,7 +72,7 @@ module.exports = function(callback) {
 
   Object.keys(Metadata)
     .filter(key => Metadata[key].language === 'en')
-    .map(key => {
+    .forEach(key => {
       let doc = Metadata[key];
       let docUrl = utils.getPath(doc.permalink, siteConfig.cleanUrl);
       let links = enabledLanguages.map(lang => {
@@ -94,7 +90,7 @@ module.exports = function(callback) {
   const sm = sitemap.createSitemap({
     hostname: siteConfig.url,
     cacheTime: 600 * 1000, // 600 sec - cache purge period
-    urls: urls,
+    urls,
   });
 
   sm.toXML((err, xml) => {
diff --git a/lib/server/translate-plugin.js b/lib/server/translate-plugin.js
index 99248986a96f..4cf1fcd157a3 100644
--- a/lib/server/translate-plugin.js
+++ b/lib/server/translate-plugin.js
@@ -25,8 +25,8 @@ module.exports = function translatePlugin(babel) {
             description = attributes[i].value.value;
           }
         }
-        /* use an expression container if inside a jsxelement */
-        if (path.findParent(path => true).node.type === 'JSXElement') {
+        /* use an expression container if inside a JSXElement */
+        if (path.findParent(() => true).node.type === 'JSXElement') {
           path.replaceWith(
             t.jSXExpressionContainer(
               t.callExpression(t.identifier('translate'), [
diff --git a/lib/server/versionFallback.js b/lib/server/versionFallback.js
index 01a5aa914727..be11819da188 100644
--- a/lib/server/versionFallback.js
+++ b/lib/server/versionFallback.js
@@ -96,7 +96,7 @@ files.forEach(file => {
 
 // returns the version to use for a document based on its id and
 // what the requested version is
-function docVersion(id, req_version) {
+function docVersion(id, reqVersion) {
   if (!available[id]) {
     return null;
   }
@@ -104,13 +104,10 @@ function docVersion(id, req_version) {
   // is found, then check if that version has an available file to use
   let requestedFound = false;
   for (let i = 0; i < versions.length; i++) {
-    if (versions[i] === req_version) {
+    if (versions[i] === reqVersion) {
       requestedFound = true;
     }
-    if (!requestedFound) {
-      continue;
-    }
-    if (available[id].has(versions[i])) {
+    if (requestedFound && available[id].has(versions[i])) {
       return versions[i];
     }
   }
@@ -243,18 +240,16 @@ function docData() {
 }
 
 // return the version of the sidebar to use given a requested version
-function sidebarVersion(req_version) {
+function sidebarVersion(reqVersion) {
   // iterate through versions until a version less than or equal to the requested
   // is found, then check if that version has an available file to use
   let requestedFound = false;
   for (let i = 0; i < versions.length; i++) {
-    if (versions[i] === req_version) {
+    if (versions[i] === reqVersion) {
       requestedFound = true;
     }
-    if (!requestedFound) {
-      continue;
-    }
     if (
+      requestedFound &&
       fs.existsSync(
         CWD + '/versioned_sidebars/version-' + versions[i] + '-sidebars.json'
       )
@@ -263,7 +258,7 @@ function sidebarVersion(req_version) {
     }
   }
   throw new Error(
-    `No sidebar file available to use for version ${req_version}. Verify that 'version-${req_version}-sidebars.json' exists.`
+    `No sidebar file available to use for version ${reqVersion}. Verify that 'version-${reqVersion}-sidebars.json' exists.`
   );
 }
 
diff --git a/lib/start-server.js b/lib/start-server.js
index 7e91eac2414a..cf940ec15fbd 100755
--- a/lib/start-server.js
+++ b/lib/start-server.js
@@ -18,13 +18,12 @@ require('babel-register')({
   presets: ['react', 'env'],
 });
 
-// For verifying port usage
-const tcpPortUsed = require('tcp-port-used');
-
-// initial check that required files are present
 const chalk = require('chalk');
 const fs = require('fs');
+const program = require('commander');
 const openBrowser = require('react-dev-utils/openBrowser');
+const tcpPortUsed = require('tcp-port-used');
+
 const CWD = process.cwd();
 const env = require('./server/env.js');
 
@@ -40,8 +39,6 @@ if (env.versioning.enabled && env.versioning.missingVersionsPage) {
   process.exit(1);
 }
 
-const program = require('commander');
-
 program
   .option('--port <number>', 'Specify port number')
   .option('--no-watch', 'Toggle live reload file watching')
@@ -50,7 +47,6 @@ program
 let port = parseInt(program.port, 10) || process.env.PORT || 3000;
 let numAttempts = 0;
 const MAX_ATTEMPTS = 10;
-checkPort();
 
 function checkPort() {
   tcpPortUsed
@@ -84,3 +80,5 @@ function checkPort() {
       }, 0);
     });
 }
+
+checkPort();
diff --git a/lib/version.js b/lib/version.js
index 1cfa7221af81..a4a2d0e07441 100755
--- a/lib/version.js
+++ b/lib/version.js
@@ -7,11 +7,13 @@
  * LICENSE file in the root directory of this source tree.
  */
 
+const program = require('commander');
+const chalk = require('chalk');
 const glob = require('glob');
 const fs = require('fs-extra');
-const path = require('path');
 const mkdirp = require('mkdirp');
-const chalk = require('chalk');
+const path = require('path');
+
 const readMetadata = require('./server/readMetadata.js');
 const utils = require('./server/utils.js');
 const versionFallback = require('./server/versionFallback.js');
@@ -28,7 +30,6 @@ if (fs.existsSync(CWD + '/versions.json')) {
 
 let version;
 
-const program = require('commander');
 program
   .arguments('<version>')
   .action(ver => {
@@ -130,16 +131,18 @@ if (versionFallback.diffLatestSidebar()) {
   const versioned = {};
 
   Object.keys(sidebar).forEach(sb => {
-    const version_sb = 'version-' + version + '-' + sb;
-    versioned[version_sb] = {};
+    const versionSidebar = 'version-' + version + '-' + sb;
+    versioned[versionSidebar] = {};
 
     const categories = sidebar[sb];
     Object.keys(categories).forEach(category => {
-      versioned[version_sb][category] = [];
+      versioned[versionSidebar][category] = [];
 
       const ids = categories[category];
-      ids.forEach((id, index) => {
-        versioned[version_sb][category].push('version-' + version + '-' + id);
+      ids.forEach(id => {
+        versioned[versionSidebar][category].push(
+          'version-' + version + '-' + id
+        );
       });
     });
   });
diff --git a/lib/write-translations.js b/lib/write-translations.js
index c7826c428bce..46ebaf169f96 100755
--- a/lib/write-translations.js
+++ b/lib/write-translations.js
@@ -9,15 +9,16 @@
 
 /* generate the i18n/en.json file */
 
-const CWD = process.cwd();
+const traverse = require('babel-traverse').default;
+const babylon = require('babylon');
 const fs = require('fs-extra');
-const mkdirp = require('mkdirp');
 const glob = require('glob');
+const mkdirp = require('mkdirp');
+const nodePath = require('path');
+
 const readMetadata = require('./server/readMetadata.js');
-const path = require('path');
+const CWD = process.cwd();
 const siteConfig = require(CWD + '/siteConfig.js');
-const babylon = require('babylon');
-const traverse = require('babel-traverse').default;
 const sidebars = require(CWD + '/sidebars.json');
 
 let customTranslations = {
@@ -46,10 +47,10 @@ function execute() {
   };
 
   // look through markdown headers of docs for titles and categories to translate
-  const docsDir = path.join(CWD, '../', readMetadata.getDocsPath());
+  const docsDir = nodePath.join(CWD, '../', readMetadata.getDocsPath());
   let files = glob.sync(CWD + '/../' + readMetadata.getDocsPath() + '/**');
   files.forEach(file => {
-    const extension = path.extname(file);
+    const extension = nodePath.extname(file);
     if (extension === '.md' || extension === '.markdown') {
       let res;
       try {
@@ -115,7 +116,7 @@ function execute() {
   // go through pages to look for text inside translate tags
   files = glob.sync(CWD + '/pages/en/**');
   files.forEach(file => {
-    const extension = path.extname(file);
+    const extension = nodePath.extname(file);
     if (extension === '.js') {
       const ast = babylon.parse(fs.readFileSync(file, 'utf8'), {
         plugins: ['jsx'],
diff --git a/website/pages/en/about-slash.js b/website/pages/en/about-slash.js
index 29d1855fbdad..2fef9452f6d8 100644
--- a/website/pages/en/about-slash.js
+++ b/website/pages/en/about-slash.js
@@ -5,39 +5,66 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-const React = require("react");
-const CompLibrary = require("../../core/CompLibrary.js");
+/* eslint-disable react/jsx-no-comment-textnodes */
+
+const React = require('react');
+const CompLibrary = require('../../core/CompLibrary.js');
 const Container = CompLibrary.Container;
-const GridBlock = CompLibrary.GridBlock;
-const siteConfig = require(process.cwd() + "/siteConfig.js");
-const translate = require("../../server/translate.js").translate;
+const siteConfig = require(process.cwd() + '/siteConfig.js');
+const translate = require('../../server/translate.js').translate;
 
 class AboutSlash extends React.Component {
   render() {
     return (
       <div className="pageContainer">
         <Container className="mainContainer documentContainer postContainer">
-          <h1><translate>About Slash</translate></h1>
-          <img src={`${siteConfig.baseUrl}img/docusaurus.svg`} alt="Docusaurus"/>
+          <h1>
+            <translate>About Slash</translate>
+          </h1>
+          <img
+            src={`${siteConfig.baseUrl}img/docusaurus.svg`}
+            alt="Docusaurus"
+          />
           <p>
-            Slash is the official mascot of Docusaurus. You will find different variations of her throughout the <a href="https://docusaurus.io">website</a>, whether she is moving fast on her scooter or writing documentation at her standing desk. At Facebook, we have actual Slash plushies -- and you never know, you may see these plushies at various events and conferences in the future.
+            Slash is the official mascot of Docusaurus. You will find different
+            variations of her throughout the{' '}
+            <a href="https://docusaurus.io">website</a>, whether she is moving
+            fast on her scooter or writing documentation at her standing desk.
+            At Facebook, we have actual Slash plushies -- and you never know,
+            you may see these plushies at various events and conferences in the
+            future.
           </p>
         </Container>
         <Container className="mainContainer">
-          <h2><translate>Birth of Slash</translate></h2>
-          <img src={`${siteConfig.baseUrl}img/slash-birth.png`} alt="Birth of Slash"/>
+          <h2>
+            <translate>Birth of Slash</translate>
+          </h2>
+          <img
+            src={`${siteConfig.baseUrl}img/slash-birth.png`}
+            alt="Birth of Slash"
+          />
           <p>
-            The team sat in a conference room trying to come up with a name for the project. Dinosaurs became a theme, finally landing on Docusaurus, combining documentation with those many dinosaurs that end in "saurus". Of course, we needed a logo for our new project. Eric sat down and designed a logo that was quite beyond the norm of our normal open source project logos, but yet was just so awesome, we had to use it. We needed a name for this cute Docusaur. "Marky" for markdown? "Docky" for documentation? No, "Slash" for the normal way someone starts code documentation in many programming languages <code>//</code> or <code>/*</code> or <code>///</code>. And Slash was born.
+            The team sat in a conference room trying to come up with a name for
+            the project. Dinosaurs became a theme, finally landing on
+            Docusaurus, combining documentation with those many dinosaurs that
+            end in "saurus". Of course, we needed a logo for our new project.
+            Eric sat down and designed a logo that was quite beyond the norm of
+            our normal open source project logos, but yet was just so awesome,
+            we had to use it. We needed a name for this cute Docusaur. "Marky"
+            for markdown? "Docky" for documentation? No, "Slash" for the normal
+            way someone starts code documentation in many programming languages{' '}
+            <code>//</code> or <code>/*</code> or <code>///</code>. And Slash
+            was born.
           </p>
         </Container>
-        <br/>
+        <br />
       </div>
     );
   }
 }
 
 AboutSlash.defaultProps = {
-  language: "en"
+  language: 'en',
 };
 
 AboutSlash.title = 'About Slash';
diff --git a/website/pages/en/index.js b/website/pages/en/index.js
index 88086a9e166d..e2a0735c4c3c 100755
--- a/website/pages/en/index.js
+++ b/website/pages/en/index.js
@@ -9,7 +9,6 @@ const React = require('react');
 const CompLibrary = require('../../core/CompLibrary.js');
 const Container = CompLibrary.Container;
 const GridBlock = CompLibrary.GridBlock;
-const MarkdownBlock = CompLibrary.MarkdownBlock; /* Used to read markdown */
 const siteConfig = require(process.cwd() + '/siteConfig.js');
 const translate = require('../../server/translate.js').translate;
 
@@ -74,17 +73,11 @@ class HomeSplash extends React.Component {
 class Index extends React.Component {
   render() {
     let language = this.props.language || 'en';
-    const showcase = siteConfig.users
-      .filter(user => {
-        return user.pinned;
-      })
-      .map((user, i) => {
-        return (
-          <a href={user.infoLink} key={i}>
-            <img src={user.image} alt={user.caption} title={user.caption} />
-          </a>
-        );
-      });
+    const showcase = siteConfig.users.filter(user => user.pinned).map(user => (
+      <a href={user.infoLink} key={user.infoLink}>
+        <img src={user.image} alt={user.caption} title={user.caption} />
+      </a>
+    ));
 
     return (
       <div>
diff --git a/website/pages/en/users.js b/website/pages/en/users.js
index edee6dc8d1df..67525605f92c 100644
--- a/website/pages/en/users.js
+++ b/website/pages/en/users.js
@@ -12,9 +12,9 @@ const siteConfig = require(process.cwd() + '/siteConfig.js');
 const translate = require('../../server/translate.js').translate;
 
 class Users extends React.Component {
-  renderUser(user, i) {
+  renderUser(user) {
     return (
-      <a href={user.infoLink} key={i}>
+      <a href={user.infoLink} key={user.infoLink}>
         <img src={user.image} alt={user.caption} title={user.caption} />
       </a>
     );
diff --git a/website/static/js/code-blocks-buttons.js b/website/static/js/code-blocks-buttons.js
index 50924cba7e1a..052a8fa7c4dc 100644
--- a/website/static/js/code-blocks-buttons.js
+++ b/website/static/js/code-blocks-buttons.js
@@ -4,6 +4,7 @@ window.addEventListener('load', function() {
   function button(label, ariaLabel, icon, className) {
     const btn = document.createElement('button');
     btn.classList.add('btnIcon', className);
+    btn.setAttribute('type', 'button');
     btn.setAttribute('aria-label', ariaLabel);
     btn.innerHTML =
       '<div class="btnIcon__body">' +
@@ -11,8 +12,7 @@ window.addEventListener('load', function() {
       '<strong class="btnIcon__label">' +
       label +
       '</strong>' +
-      '</div>' +
-      '</button>';
+      '</div>';
     return btn;
   }