JavaScript Program to Update the Value for a Specific Key in Map

In this article, we will see different approaches to update the value for a specific key in Map in JavaScript. JavaScript Map is a collection of key-value pairs. We have different methods to access a specific key in JavaScript Map.

Methods to update the value for a specific key in Map in JavaScript

• Using the JavaScript Map set() Method
• Using Map.forEach() Method

Method 1: Using JavaScript Map.set() method

In this method, we will use the built-in Map.set() method to update the value for a specific key.

Example: In this example. we will update the value of key(‘b’) in the given map using the map.set() method.

Javascript

let m = new Map([
      ["a", 100],
      ["b", 200],
]);

console.log("Old value for key: 'b', "+m.get('b'));
m.set('b',1000)
console.log("New value for key: 'b', "+m.get('b'));

Output

Old value for key: 'b', 200
New value for key: 'b', 1000

Method 2: Using Map.forEach() method

In this method, we will iterate the map using map.forEach() method to iterate the key-value pairs and update the value for specific key.

Example: In this example, we will iterate map using forEach method and update the value for a specific key using if condition.

Javascript

// Creating a map object
let m = new Map([
    ["a", 100],
    ["b", 200],
]);

// Display old value
console.log("Old value for key: 'b', " + m.get("b"));


// Iterate and change the required value
m.forEach((value, key) => {
    if (key == "b") m.set(key, 1000);
});

// Display updated value
console.log("New value for key: 'b', " + m.get("b"));

Output

Old value for key: 'b', 200
New value for key: 'b', 1000