How do you create a new Map object in JavaScript?

In JavaScript, you can create a new Map object using the Map() constructor function.

A Map object is a collection of key-value pairs where the keys can be of any type, including objects, and the values can be of any type as well. This makes Maps a very flexible data structure that can be used in a variety of scenarios.

Here are some basic usecases of Map object:

Declare a new Map variable:

The first step is to declare a new variable to hold your Map object. You can do this using the const, let, or var keywords depending on your needs.

For example:

const myMap = new Map();

This creates a new Map object called "myMap". Note that you must use the "new" keyword to create a new Map object.

Add key-value pairs to the Map:

Now that you have declared your Map object, you can start adding key-value pairs to it. You can do this using the set() method on your Map object. The set() method takes two arguments: the key and the value.

For example, let’s say you want to create a Map that stores the names and ages of some people. You could do this like so:

const myMap = new Map();
myMap.set("John", 30);
myMap.set("Jane", 25);
myMap.set("Bob", 40);

This creates a new Map object called "myMap" and adds three key-value pairs to it. The keys are the names "John", "Jane", and "Bob", and the values are their respective ages.

Retrieve values from the Map:

Now that you have added some key-value pairs to your Map, you can retrieve the values using the get() method. The get() method takes one argument: the key you want to retrieve the value for.

For example, let’s say you want to retrieve the age of "John" from your Map. You could do this like so:

const myMap = new Map();
myMap.set("John", 30);
myMap.set("Jane", 25);
myMap.set("Bob", 40);

const johnsAge = myMap.get("John");
console.log(johnsAge); // Output: 30

This retrieves the value associated with the key "John" and stores it in a variable called "johnsAge". The value is then logged to the console.

Check if a key exists in the Map:

You can check if a key exists in your Map using the has() method. The has() method takes one argument: the key you want to check for.

For example, let’s say you want to check if the key "John" exists in your Map. You could do this like so:

const myMap = new Map();
myMap.set("John", 30);
myMap.set("Jane", 25);
myMap.set("Bob", 40);

const johnExists = myMap.has("John");
console.log(johnExists); // Output: true

This checks if the key "John" exists in your Map and stores the result in a variable called "johnExists". The result is then logged to the console.

Remove a key-value pair from the Map:

You can remove a key-value pair from your Map using the delete() method. The delete() method takes one argument: the key you want to remove.

For example, let’s say you want to remove the key-value pair for "Jane" from your Map. You could do this like so:

const myMap = new Map();
myMap.set("John", 30);
myMap.set("Jane", 25);
myMap.set("Bob", 40);

myMap.delete("Jane");
console.log(myMap); // Output: Map { 'John' => 30, 'Bob' => 40 }

This removes the key-value pair for "Jane" from your Map using the delete() method. The resulting Map object is then logged to the console.

Get the number of key-value pairs in the Map:

You can get the number of key-value pairs in your Map using the size property. The size property is a read-only property that returns the number of elements in the Map object.

For example, let’s say you want to get the number of key-value pairs in your Map. You could do this like so:

const myMap = new Map();
myMap.set("John", 30);
myMap.set("Jane", 25);
myMap.set("Bob", 40);

const mapSize = myMap.size;
console.log(mapSize); // Output: 3

This gets the number of key-value pairs in your Map using the size property and stores the result in a variable called "mapSize". The result is then logged to the console.