In computer science, an associative array, map, symbol table, or dictionary is an abstract data type composed of a collection of (key, value) pairs, such that each possible key appears at most once in the collection. Note that a dictionary is also known as a map.The dictionary problem is a classic computer science problem: the task of designing a data structure that maintains a set of data during 'search', 'delete', and 'insert' operations. There are many different types of implementations of dictionaries. Hash Table implementation Tree-Based Implementation (Self-balancing and Unbalanced trees) List based implementationWhen to use a DictionaryDictionaries are not a silver bullet ... Read More

Here is the complete implementation of the MySet class. Exampleclass MySet {    constructor() {       this.container = {};    }    display() {       console.log(this.container);    }    has(val) {       return this.container.hasOwnProperty(val);    }    add(val) {       if (!this.has(val)) {          this.container[val] = val;          return true;       }       return false;    }    delete(val) {       if (this.has(val)) {          delete this.container[val];          return true;       }   ... Read More

The difference of 2 sets means the set being subtracted should have all its elements removed from the set it is being subtracted from. So we can iterate over the second set and remove all the elements present in it from the first set. Examplestatic difference(s1, s2) {    if (!s1 instanceof MySet || !s2 instanceof MySet) {       console.log("The given objects are not of type MySet");       return null;    }    let newSet = new MySet();    s1.forEach(elem => newSet.add(elem));    s2.forEach(elem => newSet.delete(elem));    return newSet; }You can test this using − Exampleconst testSet1 = ... Read More

The operation of adding 2 sets is known as a union. You need to add every object from one set to another while checking for duplicates. We can just use the 2 methods we already implemented to implement this method.We'll implement this function as a static function as we don’t want to mutate existing sets, but create and return a new one. We first need to check if the object passed to it is really an instance of the MySet class. Examplestatic union(s1, s2) {    if (!s1 instanceof MySet || !s2 instanceof MySet) {       console.log("The given objects ... Read More

In the set that we implemented, we can create a for each function in our class and accept a callback that we can call on every element. Let's see how we can implement such a function − ExampleforEach(callback) {    for (let prop in this.container) {       callback(prop);    } }You can test this using − Exampleconst testSet = new MySet(); testSet.add(1); testSet.add(2); testSet.add(5); testSet.forEach(elem => console.log(`Element is ${elem}`));OutputThis will give the output −Element is 1 Element is 2 Element is 5The ES6 Set API also provides the same functionality using the forEach method.

The clear method is pretty straightforward. We can just reassign the container variable to a new object and the set will now be empty. This can be implemented as follows − Exampleclear() {    this.container = {}; }You can test this using −Exampleconst testSet = new MySet(); testSet.add(1); testSet.add(2); testSet.add(5); testSet.display(); testSet.clear(); testSet.display();OutputThis will give the output −{ '1': 1, '2': 2, '5': 5 } { }

The delete method checks if a value already exists in the set, if it does, then it removes that value from the set. We can implement it as follows &minusl Exampledelete(val) {    if (this.has(val)) {       delete this.container[val];       return true;    }    return false; }You can test this using − Exampleconst testSet = new MySet(); testSet.add(1); testSet.add(2); testSet.add(5); testSet.delete(5); testSet.delete(2); testSet.display(); console.log(testSet.has(5)); console.log(testSet.has(20)); console.log(testSet.has(1));OutputThis will give the output −{ '1': 1} False False TrueIn ES6, you use the delete function as follows − Exampleconst testSet = new MySet(); testSet.add(1); testSet.add(2); testSet.add(5); testSet.delete(5); ... Read More

In JavaScript, a Set is an object that is used to store a collection of unique elements of different types, such as numbers, strings, booleans, and object references, etc. const mySet = new Set(); Adding Elements to a JavaScript Set We can add elements to a JavaScript set in the following ways: Using Simple add() Method Using Method Chaining with add() Using add() Method The add() method of the Set object accepts a value as a parameter and adds it to the elements of the current Set object, and returns ... Read More

Let's create a MySet class so that it doesn't hide the actual set class in JS. We'll create a container object that'll keep track of all our values that we add to the set. We'll also create a display function that prints the set for us. Exampleclass MySet {    constructor() {       this.container = {};    }    display() {       console.log(this.container);    } }In ES6, you can directly create a set using the Set class. For example,  Exampleconst set1 = new Set(); const set2 = new Set([1, 2, 5, 6]);Checking for membershipThe has method checks ... Read More

Whenever you want to store unique elements in a container for which the order doesn't matter and you mainly want to use it to check for membership of different objects.Sets are also useful when you want to perform operations like union, intersection, a difference like you do in mathematical sets.Let's look at both how we can define our own set and use the existing one in ES6.Methods we'll implementThe ES6 set API provides some methods. We'll implement these methods in our implementation and also look at how to use them using the built-in class.add() −  Adds a new element to the ... Read More