JavaScript(JS) Map

In JavaScript, a Map is a built-in data structure that allows you to store key-value pairs. It is similar to an object, but with a few key differences.

One of the main differences between a Map and an object is that a Map can use any value as a key, whereas object keys are limited to strings and symbols. Additionally, a Map preserves the order of its entries, whereas object properties are unordered.

Here are some examples of using a Map in JavaScript:

1. Creating a Map:

let myMap = new Map();

This creates a new empty Map instance.

2. Adding and retrieving values from a Map:

let myMap = new Map();

myMap.set("key1", "value1");
myMap.set("key2", "value2");

console.log(myMap.get("key1")); // output: "value1"
console.log(myMap.get("key2")); // output: "value2"

In this example, we add two key-value pairs to the Map using the set() method, and then retrieve the values using the get() method.

3. Iterating over a Map:

let myMap = new Map();

myMap.set("key1", "value1");
myMap.set("key2", "value2");

for (let [key, value] of myMap) {
  console.log(key, value);
}

In this example, we use a for...of loop to iterate over the entries in the Map and log each key-value pair to the console.

4. Checking if a Map contains a key:

let myMap = new Map();

myMap.set("key1", "value1");
myMap.set("key2", "value2");

console.log(myMap.has("key1")); // output: true
console.log(myMap.has("key3")); // output: false

In this example, we use the has() method to check if the Map contains a key.