Hashtable

.eslintrc.json

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+{
+    "env": {
+      "browser": true,
+      "node": true,
+      "commonjs": true,
+      "jest": true,
+      "es6": true
+    },
+    "globals": {
+      "err": true,
+      "req": true,
+      "res": true,
+      "next": true
+    },
+    "extends": "eslint:recommended",
+    "parserOptions": {
+      "sourceType": "module"
+    },
+    "rules": {
+      "no-console": "off",
+      "indent": [ "error", 2 ],
+      "quotes": ["error", "single", { "allowTemplateLiterals": true }],
+      "comma-dangle": ["error", "always-multiline"],
+      "semi": [ "error", "always" ]
+    }
+  }
+

README.md

@@ -1,6 +1,19 @@
-# Table of Contents
-[1- code challange class 2 array shift ](https://github.com/Goorob-401-advanced-javascript/data-structures-and-algorithms/pull/3)
+# Hashtables
+
+## Challenge
+Implement a Hashtable with the following methods:
+
+- add: takes in both the key and value. This method should hash the key, and add the key and value pair to the table, handling collisions as needed.
+- get: takes in the key and returns the value from the table.
+- contains: takes in the key and returns a boolean, indicating if the key exists in the table already.
+- hash: takes in an arbitrary key and returns an index in the collection.
+
+## Approach & Efficiency
+- add  Time - O(1)
+- get  Time - O(1)
+- contains
+Time - O(1)
+Space - O(1)
+## API
 
-[2- code challange class 3 array binary search ](https://github.com/Goorob-401-advanced-javascript/data-structures-and-algorithms/pull/2)
 
-[

challanges/hashTable/hashTable.js

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+'use strict';
+class Hashmap {
+  constructor(size){
+    this.arr = new Array(size);
+    this.size = size;
+  }
+
+  hash(key){
+    return  key.split('').reduce((acc, val) => {
+      return acc + val.charCodeAt(0);
+    }, 0) * 19 % this.size;
+  }
+
+  add(key, val){
+    let index = this.hash(key);
+
+    if(!this.arr[index]){
+      this.arr[index] = [];
+    }
+
+    this.arr[index].push([key,val]);
+    return index;
+  }
+
+  get(key){
+    const hashed = this.hash(key);
+    const array = this.arr[hashed];
+    if(array === null || array === undefined){
+      return null;
+    }
+
+    for(let i = 0; i < array.length; i++){
+      if(array[i][0] === key){
+        return array[i][1];
+      }
+    }
+    return null;
+  }
+
+  contains(key){
+    const hashed = this.hash(key);
+    const array = this.arr[hashed];
+    if(array === null || array === undefined){
+      return false;
+    }
+
+    for(let i = 0; i < array.length; i++){
+      if(array[i][0] === key){
+        return true;
+      }
+
+    }
+    return false;
+  }
+}
+
+module.exports = Hashmap;
+

challanges/hashTable/hashTable.test.js

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+'use strict ';
+
+const Hashmap = require('./hashTable.js');
+
+describe('Hashmap', () => {
+  it('add ', () => {
+    const hashmap = new Hashmap(1024);
+    hashmap.add('name', 'angel');
+    expect(hashmap.contains('name')).toBe(true);
+  });
+
+
+  it('Successfully handle a collision within the hashtable', () => {
+    const hashmap = new Hashmap(1024);
+    hashmap.add('name', 'angel');
+    hashmap.add('class', '401');
+    expect(hashmap.get('class')).toBe('401');
+  });
+});