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Author: Isutary

hashtable.js

@@ -0,0 +1,103 @@
+let hashTable = {
+    setup: function (length) {
+        // helper function for ensuring length of hash table is prime
+        function nextPrime (num) {
+            function isPrime(n) {
+                if (n <= 1) throw new Error("Length must be greater then 1!");
+                for (let i=2; i<=Math.sqrt(n); i++) {
+                    if (n % i == 0) return false;
+                }
+                return true;
+            }
+            while (!isPrime(num)) num++;
+            return num;
+        }
+
+        this.length = nextPrime(length);
+        this.numberOfElements = 0;
+        this.table = [];
+        for (let i = 0; i < this.length; i++) this.table[i] = [];
+    },
+    hashFunction: function (input) {
+        let sum = 0;
+        input = input.toLowerCase();
+        for (let i = 1; i < input.length; i++) {
+            sum += input.charCodeAt(i) - 96;
+        }
+        return sum % this.length;
+    },
+    put: function (key, value = key) {
+        // helper function for resizing hash table when # of elements equals the length of table
+        function resize(table) {
+            let oldTable = JSON.parse(JSON.stringify(table));
+            Object.setPrototypeOf(oldTable, table);
+            table.setup(2*table.length);
+            for (let element of oldTable) {
+                table.put(element.key, element.value);
+            }
+        }
+
+        if (this.numberOfElements >= this.length) resize(this); 
+        let index = this.hashFunction(key);
+        this.table[index].push({
+            key: key,
+            value: value
+        });
+        this.numberOfElements++;
+    },
+    includes: function (key) {
+        let index = this.hashFunction(key);
+        for (let element of this.table[index]) {
+            if (element.key == key) return true;
+        }
+        return false;
+    },
+    find: function (key) {
+        let index = this.hashFunction(key);
+        for (let element of this.table[index]) {
+            if (element.key == key) return element.value;
+        }
+    },
+    remove: function (key) {
+        let index = this.hashFunction(key);
+        for (let i=0; i<this.table[index].length; i++) {
+            if (this.table[index][i].key == key) {
+                this.table[index].splice(i, 1);
+                this.numberOfElements--;
+                return true;
+            }
+        }
+        return false;
+    },
+    clear: function () {
+        this.setup(this.length);
+    },
+    [Symbol.iterator]: function() {
+        let i=0, j=0;
+        let self = this;
+        return {
+            [Symbol.iterator]() { return this; },
+            next: function next () {
+                if (j < self.table[i].length) {
+                    j++;
+                    return {
+                        value: self.table[i][j-1],
+                        done: false
+                    }
+                }
+                else if (i < self.table.length - 1) {
+                    i++;
+                    j = 0;
+                    return next();
+                }   
+                else {
+                    return {
+                        done: true
+                    }
+                }
+            }
+        }
+    }
+}
+
+export default hashTable;