Creating Dictionary using Javascript

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. 

Example

class MyMap {
   constructor() {
      this.container = {};
   }
   display() {
      console.log(this.container);
   }
}

In ES6, you can directly create a dictionary using the Map class. For example, 

Example

const map1 = new Map();
const map2 = new Map([
   ["key1", "value1"],
   ["key2", "value2"]
]);

Checking if a key existing

We need to define the hasKey method so that we can check if a key is already there. We will use this method while removing elements and setting new values. 

Exaample

hasKey(key) {
   return key in this.container;
}

In ES6, you can check if a key exists in a map using the has method. For example, 

Example

const myMap = new Map([
   ["key1", "value1"],
   ["key2", "value2"]
]);
console.log(myMap.has("key1"))
console.log(myMap.has("key3"))

Output

This will give the output −

True
False