feat: add dom helper module

Author: wewoor

src/common/dom.ts

@@ -0,0 +1,52 @@
+export type HTMLElementType = HTMLElement | null;
+export const select = document.querySelector.bind(document);
+export const selectAll = document.querySelectorAll.bind(document);
+
+export interface IPosition {
+    x: number;
+    y: number;
+}
+
+/**
+ * Get Document Rectangle info
+ */
+export function getDocumentRect() {
+    const body = document.body;
+    const html = document.documentElement;
+
+    const height = Math.max( body.scrollHeight, body.offsetHeight,
+        html.clientHeight, html.scrollHeight, html.offsetHeight );
+
+    const width = Math.max( body.scrollWidth, body.offsetWidth,
+        html.clientWidth, html.scrollWidth, html.offsetWidth );
+
+    return {
+        height,
+        width,
+    };
+}
+
+/**
+ * Returns the position of element relative anchor's position
+ * @param element target element
+ * @param anchorPos anchor's position
+ */
+export function getRelativePosition(element: HTMLElement, anchorPos: IPosition) {
+    const page = getDocumentRect();
+    const anchorX = anchorPos.x;
+    const anchorY = anchorPos.y;
+
+    const marginRight = page.width - anchorX;
+    const marginBottom = page.height - anchorY;
+
+    const viewHeight = element.offsetHeight;
+    const viewWidth = element.offsetWidth;
+
+    const x = marginRight < viewWidth ? anchorX - viewWidth : anchorX;
+    const y = marginBottom < viewHeight ? anchorY - viewHeight : anchorY;
+
+    return {
+        x,
+        y,
+    };
+}