How to Check if Two Maps are Equal in JavaScript

How to Check if Two Maps are Equal in JavaScript ?

Answer

To check if two maps are equal in JavaScript, you need to compare their sizes and iterate over the key-value pairs to ensure they match. This method provides a straightforward way to determine if two maps contain the same elements.

✐ Examples

1 Checking Equality of Two Maps by Iterating Over Key-Value Pairs

We can check if two maps are equal in JavaScript by comparing their sizes and iterating over the key-value pairs to ensure they match.

For example,

We start by declaring and initializing two maps named map1 and map2 with some key-value pairs. In this example, the maps have string keys and integer values.
We check if the sizes of map1 and map2 are equal. If their sizes are not equal, the maps are not equal.
If their sizes are equal, we iterate over the key-value pairs of map1 and check if each key-value pair exists in map2 and matches the corresponding value.
We print the result to the console using the console.log function to indicate whether the maps are equal or not.

JavaScript Program

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

// Check if the maps are equal
let equal = true;
if (map1.size !== map2.size) {
    equal = false;
} else {
    for (let [key, value] of map1) {
        if (!map2.has(key) || map2.get(key) !== value) {
            equal = false;
            break;
        }
    }
}

if (equal) {
    console.log('Maps are equal');
} else {
    console.log('Maps are not equal');
}

Output

Maps are equal

2 Checking Equality of Two Maps with Different Sizes

We can also check if two maps with different sizes are equal in JavaScript by comparing their sizes first and then iterating over the key-value pairs to ensure they match.

For example,

We start by declaring and initializing two maps named map1 and map2 with some key-value pairs. In this example, the maps have string keys and integer values, and they have different sizes.
We check if the sizes of map1 and map2 are equal. If their sizes are not equal, the maps are not equal.
If their sizes are equal, we iterate over the key-value pairs of map1 and check if each key-value pair exists in map2 and matches the corresponding value.
We print the result to the console using the console.log function to indicate whether the maps are equal or not.

JavaScript Program

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

// Check if the maps are equal
let equal = true;
if (map1.size !== map2.size) {
    equal = false;
} else {
    for (let [key, value] of map1) {
        if (!map2.has(key) || map2.get(key) !== value) {
            equal = false;
            break;
        }
    }
}

if (equal) {
    console.log('Maps are equal');
} else {
    console.log('Maps are not equal');
}

Output

Maps are not equal

3 Checking Equality of Two Maps Using a Helper Function

We can create a helper function to check if two maps are equal in JavaScript, which provides a reusable way to compare maps.

For example,

We start by declaring and initializing two maps named map1 and map2 with some key-value pairs. In this example, the maps have string keys and integer values.
We define a helper function named areMapsEqual that takes two maps as parameters and returns a boolean value indicating whether the maps are equal.
Inside the helper function, we compare the sizes of the maps. If their sizes are not equal, we return false.
If their sizes are equal, we iterate over the key-value pairs of map1 and check if each key-value pair exists in map2 and matches the corresponding value, returning true if they do.
We call the helper function with map1 and map2 as arguments and print the result to the console using the console.log function to indicate whether the maps are equal or not.

JavaScript Program

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

// Helper function to check if two maps are equal
function areMapsEqual(map1, map2) {
    if (map1.size !== map2.size) {
        return false;
    }
    for (let [key, value] of map1) {
        if (!map2.has(key) || map2.get(key) !== value) {
            return false;
        }
    }
    return true;
}

// Check if the maps are equal using the helper function
if (areMapsEqual(map1, map2)) {
    console.log('Maps are equal');
} else {
    console.log('Maps are not equal');
}

Output

Maps are equal

Summary

In this tutorial, we learned How to Check if Two Maps are Equal in JavaScript language with well detailed examples.

◀ Previous Next ▶

JavaScript Tutorials

JavaScript How-Tos

How to Check if Two Maps are Equal in JavaScript