Front End Technology Articles - Page 599 of 860

We'll implement the get method that searches a given key in the dictionary. Exampleget(key) {    if(this.hasKey(key)) {       return this.container[key];    }    return undefined; }Again, JS objects are very much implemented like dictionaries, hence have most of the functionality we can use directly without any more code needed. This is also heavily optimized, so you don't have to worry about the runtime of the function.You can test this using − Exampleconst myMap = new MyMap(); myMap.put("key1", "value1"); myMap.put("key2", "value2"); console.log(myMap.get("key1")) console.log(myMap.get("key2")) console.log(myMap.get("key3"))OutputThis will give the output −value1 value2 undefinedIn ES6, you have the same functionality using the ... Read More

To remove an element from the dictionary, we first need to check if it exists in the dictionary.We'll use the hasKey method for that. Then we can directly delete it using the delete operator.We'll return a Boolean so that the place where we call this method can know whether the key already existed or not in the dictionary. Exampledelete(key) {    if(this.hasKey(key)) {       delete this.container[key];       return true;    }    return false; }You can test this using − Exampleconst myMap = new MyMap(); myMap.put("key1", "value1"); myMap.put("key2", "value2"); myMap.display(); myMap.delete("key2"); myMap.display();OutputThis will give the output ... Read More

Now we'll create the put method that'll allow us to put key-value pairs on the dictionary. Now using this we'll implement the put method.Note that JS has objects that act quite like dictionaries. We can just set the container's key property to value. Exampleput(key, value) {    this.container[key] = value; }You can test this and the previous functions using − Exampleconst myMap = new MyMap() myMap.put("key1", "value1") myMap.put("key2", "value2") myMap.display() console.log(myMap.hasKey("key1")); console.log(myMap.hasKey("key3"));OutputThis will give the output −{key1: "value1", key2: "value2"} true falseIn ES6, you can put a key-value pair in a map using the set method. For example,  Exampleconst myMap ... Read More

Let's create a MyMap class so that it doesn't hide the actual Map class in JS. We'll create a container object that'll keep track of all our values that we add to the map. We'll also create a display function that prints the map for us. Exampleclass MyMap {    constructor() {       this.container = {};    }    display() {       console.log(this.container);    } }In ES6, you can directly create a dictionary using the Map class. For example,  Exampleconst map1 = new Map(); const map2 = new Map([    ["key1", "value1"],    ["key2", "value2"] ]);Checking if ... Read More

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 } { }