How to Sort a Map in JavaScript?

Sorting a Map in JavaScript requires converting it into an array, sorting it, and then converting it back into a Map. Below are the common approaches to sort a Map based on keys or values.

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1. Using Map.entries() and sort() Method

• Converts Map.entries() into an array
• Sorts the array by keys
• Converts it back into a Map

Example: Sorting by Keys (Ascending)

let map1 = new Map([
    [4, 2],
    [2, 3]
]);

map1.set(3, 10);
console.log("Original Map:", map1);

// Sorting by keys
map1 = new Map([...map1.entries()].sort());

console.log("Sorted by Keys:");
for (let [key, value] of map1) {
    console.log(key, value);
}

Output:

Original Map: Map(3) { 4 => 2, 2 => 3, 3 => 10 }
Sorted by Keys:
2 3
3 10
4 2

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2. Using Array.from() and sort() Method

• Converts Map to an array using Array.from()
• Sorts it based on keys or values
• Converts it back to a Map

Example: Sorting by Values (Ascending)

let map1 = new Map([
    [4, 2],
    [2, 3]
]);

map1.set(3, 10);
console.log("Original Map:", map1);

// Sorting by values in ascending order
const newMap = Array.from(map1).sort((a, b) => a[1] - b[1]);

const sortedMap = new Map(newMap);
console.log("Sorted by Values:", sortedMap);

Output:

Original Map: Map(3) { 4 => 2, 2 => 3, 3 => 10 }
Sorted by Values: Map(3) { 4 => 2, 2 => 3, 3 => 10 }

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3. Using Lodash’s _.sortBy Function

• Converts Map to an array
• Uses _.sortBy() to sort based on values
• Converts back into a Map

Example: Sorting by Values (Ascending)

// Importing the lodash library
const _ = require('lodash');

let map1 = new Map([
    ['banana', 3],
    ['apple', 5],
    ['orange', 2],
]);

map1.set('grape', 10); // Adding a new element

console.log("Original Map:", map1);

// Sorting by values in ascending order
const sortedMap = new Map(_.sortBy(Array.from(map1), [(entry) => entry[1]]));

console.log("Sorted Map:", sortedMap);

Output:

Sorted Map: Map { 'orange' => 2, 'banana' => 3, 'apple' => 5, 'grape' => 10 }

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Summary

Method	Sorting Criteria	Convert Back to Map?
Map.entries() + sort()	Sorts by keys	Yes
Array.from() + sort()	Sorts by keys or values	Yes
Lodash _.sortBy()	Sorts by values	Yes

Each method is useful depending on whether you need to sort by keys or values. 🚀