feat(curriculum): add hash table lab (freeCodeCamp#56301)

client/i18n/locales/english/intro.json

@@ -2439,7 +2439,10 @@
           "For this lab, you will build a linked list class using JavaScript."
         ]
       },
-      "wraf": { "title": "265", "intro": [] },
+      "lab-hash-table-class": {
+        "title": "Build a Hash Table Class",
+        "intro": ["For this lab, you will build a hash table using JavaScript."]
+      },
       "muyw": { "title": "266", "intro": [] },
       "quiz-javascript-data-structures": {
         "title": "JavaScript Data Structures Quiz",

client/src/pages/learn/front-end-development/lab-hash-table-class/index.md

@@ -0,0 +1,9 @@
+---
+title: Introduction to the Build a Hash Table Class
+block: lab-hash-table-class
+superBlock: front-end-development
+---
+
+## Introduction to the Build a Hash Table Class
+
+For this lab, you will build a hash table using JavaScript.

curriculum/challenges/_meta/lab-hash-table-class/meta.json

@@ -0,0 +1,11 @@
+{
+  "name": "Build a Hash Table Class",
+  "isUpcomingChange": true,
+  "usesMultifileEditor": true,
+  "blockType": "lab",
+  "dashedName": "lab-hash-table-class",
+  "order": 265,
+  "superBlock": "front-end-development",
+  "challengeOrder": [{ "id": "66f1805aac05f00a7028fbcc", "title": "Build a Hash Table Class" }],
+  "helpCategory": "JavaScript"
+}

curriculum/challenges/english/25-front-end-development/lab-hash-table-class/66f1805aac05f00a7028fbcc.md

@@ -0,0 +1,221 @@
+---
+id: 66f1805aac05f00a7028fbcc
+title: Build a Hash Table Class
+challengeType: 14
+dashedName: build-a-hash-table-class
+---
+
+# --description--
+
+**Objective:** Fulfill the user stories below and get all the tests to pass to complete the lab. 
+
+**User Stories:**
+
+1. You should define a class named `HashTable` with a `collection` property initialized as an empty object inside its `constructor` method. The `collection` object should store key-value pairs based on the hashed value of the key.
+1. The `HashTable` class should have four instance methods, namely `hash`, `add`, `remove`, and `lookup`.
+1. The `hash` method should take a string as a parameter and return the hashed value computed as the sum of the UTF-16 code unit of each character in the string. Use the `charCodeAt` method for that.
+1. The `add` method should take a key-value pair as the parameters, and hash the key. The hashed value should be used to store the key-value pair inside the hash table (`collection` object). When the same hash value is produced by multiple different keys, each key-value pair should be stored using the same hash value.
+1. The `remove` method should take a key as a parameter and remove the corresponding key-value pair from the hash table. If that's the last key-value pair, it should remove the hash key as well.
+1. The `lookup` method should take a key as a parameter and return the corresponding value stored inside the hash table, or `null` if not present.
+
+# --hints--
+
+You should have a `HashTable` class.
+
+```js
+assert.isFunction(HashTable);
+assert.isObject(new HashTable());
+```
+
+Your `HashTable` class should have a `collection` property initialized as an empty object.
+
+```js
+const table = new HashTable();
+assert.isObject(table.collection);
+assert.isEmpty(table.collection);
+```
+
+Your `HashTable` class should have a `hash` method.
+
+```js
+const table = new HashTable();
+assert.isFunction(table.hash);
+```
+
+`new HashTable().hash("freeCodeCamp")` should return `1182`.
+
+```js
+const table = new HashTable();
+assert.strictEqual(table.hash("freeCodeCamp"), 1182);
+```
+
+The `hash` method should take a string as a parameter and return the hashed value computed as the sum of the UTF-16 code unit of each character in the string using the `charCodeAt` method.
+
+```js
+const table = new HashTable();
+assert.strictEqual(table.hash("Hey you"), 675);
+```
+
+Your `HashTable` class should have an `add` method.
+
+```js
+const table = new HashTable();
+assert.isFunction(table.add);
+```
+
+After calling `hashTable.add("FCC", "freeCodeCamp")`, `hashTable.collection` should become `{ 204: { FCC: 'freeCodeCamp' } }`.
+
+```js
+const table = new HashTable();
+table.add("FCC", "freeCodeCamp");
+assert.deepEqual(table.collection, { 204: { FCC: 'freeCodeCamp' } });
+```
+
+The `add` method should take a key-value pair as the parameters, hash the key and store the key-value pair inside the hashed key of the `collection` object.
+
+```js
+const table = new HashTable();
+table.add("test", "this is a test");
+assert.deepEqual(table.collection, { 448: { test: 'this is a test' } });
+```
+
+After calling `hashTable.add("FCC", "freeCodeCamp")` and `hashTable.add("CFC", "chloroflourocarbon")`, `hashTable.collection` should become `{ 204: { FCC: 'freeCodeCamp', CFC: 'chloroflourocarbon' } }`.
+
+```js
+const table = new HashTable();
+table.add("FCC", "freeCodeCamp");
+table.add("CFC", "chloroflourocarbon");
+assert.deepEqual(table.collection, { 204: { FCC: 'freeCodeCamp', CFC: 'chloroflourocarbon' } });
+```
+
+When the same hash value is produced by multiple different keys, the `add` method should store each key-value pair using the same hash value.
+
+```js
+const table = new HashTable();
+table.add("pan", "frying");
+table.add("nap", "sleeping");
+assert.deepEqual(table.collection, { 319: { pan: 'frying', nap: 'sleeping' } });
+```
+
+Your `HashTable` class should have a `remove` method.
+
+```js
+const table = new HashTable();
+assert.isFunction(table.remove);
+```
+
+When `hashtable.collection` is equal to `{ 204: { FCC: 'freeCodeCamp' } }`, `hashTable.remove("FCC")` should remove both the `FCC` key and the `204` key from the `collection` object.
+
+```js
+const table = new HashTable();
+table.add("FCC", "freeCodeCamp");
+table.remove("FCC");
+assert.isEmpty(table.collection);
+```
+
+When `hashtable.collection` is equal to `{ 204: { FCC: 'freeCodeCamp', CFC: 'chloroflourocarbon' } }`, `hashTable.remove("FCC")` should only remove the `FCC` key from the value of the key `204`.
+
+```js
+const table = new HashTable();
+table.add("FCC", "freeCodeCamp");
+table.add("CFC", "chloroflourocarbon");
+table.remove("FCC");
+assert.deepEqual(table.collection, { 204: { CFC: 'chloroflourocarbon' } });
+```
+
+The `remove` method should accept a key as input and remove both the associated key value pair and the hash key when it is empty.
+
+```js
+const table = new HashTable();
+table.add("FCC", "freeCodeCamp");
+table.remove("FCC");
+assert.isEmpty(table.collection);
+```
+
+The `remove` method should only remove the correct key value pair from the hash key object.
+
+```js
+const table = new HashTable();
+table.add("pan", "frying");
+table.add("nap", "sleeping");
+table.remove("pan");
+assert.deepEqual(table.collection, { 319: { nap: 'sleeping' } });
+```
+
+Your `HashTable` class should have a `lookup` method.
+
+```js
+const table = new HashTable();
+assert.isFunction(table.lookup);
+```
+
+`hashTable.lookup("FCC")` should return the value of the `FCC` key stored within `hashtable.collection`.
+
+```js
+const table = new HashTable();
+table.add("FCC", "freeCodeCamp");
+table.add("CFC", "chloroflourocarbon");
+assert.strictEqual(table.lookup("FCC"), "freeCodeCamp");
+```
+
+`hashTable.lookup("FCC")` should return `null` if there's no `FCC` key stored within `hashtable.collection`.
+
+```js
+const table = new HashTable();
+table.add("FCC", "freeCodeCamp");
+table.add("CFC", "chloroflourocarbon");
+assert.isNull(table.lookup("x"));
+```
+
+# --seed--
+
+## --seed-contents--
+
+```js
+
+```
+
+# --solutions--
+
+```js
+class HashTable {
+    constructor() {
+        this.collection = {};
+    }
+
+    hash(string) {
+        let hashed = 0;
+        for (let i = 0; i < string.length; i++) {
+            hashed += string.charCodeAt(i);
+        }
+        return hashed
+    }
+
+    add(key, val) {
+        const theHash = this.hash(key);
+        if (!this.collection.hasOwnProperty(theHash)) {
+            this.collection[theHash] = {};
+        }
+        this.collection[theHash][key] = val;
+    }
+
+    remove(key) {
+        const theHash = this.hash(key);
+        const hashedObj = this.collection[theHash];
+        if (hashedObj.hasOwnProperty(key)) {
+            delete hashedObj[key];
+        }
+        if (!Object.keys(hashedObj).length) {
+            delete this.collection[theHash];
+        }
+    }
+
+    lookup(key) {
+        const theHash = this.hash(key);
+        if (this.collection.hasOwnProperty(theHash)) {
+            return this.collection[theHash][key];
+        }
+        return null
+    }
+}
+```