How to Merge Two Maps in JavaScript - Step by Step Examples

How to Merge Two Maps in JavaScript ?

Answer

To merge two maps in JavaScript, you can use the spread operator to create a new map that combines the contents of both maps. This method provides a concise and convenient way to merge maps.

✐ Examples

1 Merging Two Maps Using the Spread Operator

We can merge two maps in JavaScript using the spread operator, which creates a new map that includes all key-value pairs from both maps.

For example,

We start by declaring and initializing two maps named map1 and map2 with some key-value pairs. In this example, both maps have string keys and integer values.
We create a new map named mergedMap that combines the contents of map1 and map2 using the spread operator.
We print the merged map to the console using the console.log function to verify the merge.

JavaScript Program

const map1 = new Map([
    ['one', 1],
    ['two', 2]
]);
const map2 = new Map([
    ['three', 3],
    ['four', 4]
]);

// Merge the maps using the spread operator
const mergedMap = new Map([...map1, ...map2]);

// Print the merged map
console.log('Merged Map:', Array.from(mergedMap));

Output

Merged Map: [['one', 1], ['two', 2], ['three', 3], ['four', 4]]

2 Merging Two Maps with Overlapping Keys Using the Spread Operator

We can merge two maps in JavaScript and handle overlapping keys using the spread operator. If a key exists in both maps, the value from the second map will overwrite the value in the first map.

For example,

We start by declaring and initializing two maps named map1 and map2 with some key-value pairs. In this example, both maps have string keys and integer values, and there is an overlapping key.
We create a new map named mergedMap that combines the contents of map1 and map2 using the spread operator. The value from map2 will overwrite the value from map1 for overlapping keys.
We print the merged map to the console using the console.log function to verify the merge.

JavaScript Program

const map1 = new Map([
    ['one', 1],
    ['two', 2]
]);
const map2 = new Map([
    ['two', 22],
    ['three', 3]
]);

// Merge the maps using the spread operator
const mergedMap = new Map([...map1, ...map2]);

// Print the merged map
console.log('Merged Map:', Array.from(mergedMap));

Output

Merged Map: [['one', 1], ['two', 22], ['three', 3]]

3 Merging Two Maps Using forEach Method

We can also merge two maps in JavaScript using the forEach method to add key-value pairs from one map to another. This method provides a more traditional approach to merging maps.

For example,

We start by declaring and initializing two maps named map1 and map2 with some key-value pairs. In this example, both maps have string keys and integer values.
We use the forEach method to iterate over map2 and add each key-value pair to map1 using the set method.
We print the merged map to the console using the console.log function to verify the merge.

JavaScript Program

const map1 = new Map([
    ['one', 1],
    ['two', 2]
]);
const map2 = new Map([
    ['three', 3],
    ['four', 4]
]);

// Merge map2 into map1 using forEach
map2.forEach((value, key) => {
    map1.set(key, value);
});

// Print the merged map
console.log('Merged Map:', Array.from(map1));

Output

Merged Map: [['one', 1], ['two', 2], ['three', 3], ['four', 4]]

Summary

In this tutorial, we learned How to Merge Two Maps in JavaScript language with well detailed examples.

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