JavaScript How to Convert Map to Array Easily

You can convert a Map to an array in JavaScript using Array.from(map) or the spread operator like [...map], which creates an array of key-value pairs.

Examples

Inputnew Map([[1, 'a'], [2, 'b']])

Output[[1, 'a'], [2, 'b']]

Inputnew Map([['name', 'John'], ['age', 30]])

Output[['name', 'John'], ['age', 30]]

Inputnew Map()

Output[]

How to Think About It

To convert a Map to an array, think of the Map as a collection of pairs (key and value). You want to create a list (array) where each item is one of these pairs. JavaScript provides easy ways to turn this collection into an array by extracting all pairs at once.

Algorithm

1

Get the Map object as input.

2

Use a method to extract all key-value pairs from the Map.

3

Create a new array containing these pairs.

4

Return the new array.

Code

javascript

const map = new Map([[1, 'a'], [2, 'b']]);
const arrayFromMap = Array.from(map);
console.log(arrayFromMap);

const spreadArray = [...map];
console.log(spreadArray);

Output

[[1, 'a'], [2, 'b']]
[[1, 'a'], [2, 'b']]

Dry Run

Let's trace converting Map([[1, 'a'], [2, 'b']]) to an array.

1

Start with Map

Map contains pairs: (1, 'a'), (2, 'b')

2

Use Array.from(map)

Extract pairs into array: [[1, 'a'], [2, 'b']]

3

Result

Array with pairs: [[1, 'a'], [2, 'b']]

Step	Map Content	Array Result
1	Map with (1, 'a'), (2, 'b')	N/A
2	N/A	[[1, 'a'], [2, 'b']]

Why This Works

Step 1: Map stores pairs

A Map holds data as key-value pairs, not as a list.

Step 2: Array.from extracts pairs

Array.from(map) takes all pairs and puts them into an array.

Step 3: Spread operator does the same

Using [...map] spreads all pairs into a new array.

Alternative Approaches

Using forEach to build array

javascript

const map = new Map([[1, 'a'], [2, 'b']]);
const arr = [];
map.forEach((value, key) => {
  arr.push([key, value]);
});
console.log(arr);

More manual but useful if you want to process pairs while converting.

Using map.keys() or map.values()

javascript

const map = new Map([[1, 'a'], [2, 'b']]);
const keysArray = [...map.keys()];
const valuesArray = [...map.values()];
console.log(keysArray);
console.log(valuesArray);

Extracts only keys or only values as arrays, not pairs.

Complexity: O(n) time, O(n) space

Time Complexity

Converting a Map to an array requires visiting each pair once, so it takes linear time proportional to the number of pairs.

Space Complexity

A new array is created to hold all pairs, so space used grows linearly with the Map size.

Which Approach is Fastest?

Using Array.from() or the spread operator [...map] are equally efficient and concise; manual loops are more verbose but allow custom processing.

Approach	Time	Space	Best For
Array.from(map)	O(n)	O(n)	Simple and direct conversion
[...map]	O(n)	O(n)	Concise and readable syntax
forEach loop	O(n)	O(n)	Custom processing during conversion
map.keys()/map.values()	O(n)	O(n)	Extracting only keys or values