How to Use Object.fromEntries in JavaScript: Syntax and Examples

Object.fromEntries converts an array of key-value pairs into an object. It takes an iterable like an array of arrays and returns a new object with those keys and values.

Syntax

The Object.fromEntries() method takes one argument: an iterable of key-value pairs (usually an array of arrays). It returns a new object constructed from these pairs.

• iterable: An array or any iterable where each item is a two-element array: [key, value].
• Returns: A new object with keys and values from the iterable.

javascript

const obj = Object.fromEntries(iterable);

Example

This example shows how to convert an array of key-value pairs into an object using Object.fromEntries. It creates an object with properties from the array.

javascript

const entries = [['name', 'Alice'], ['age', 30], ['city', 'Paris']];
const obj = Object.fromEntries(entries);
console.log(obj);

Output

{"name":"Alice","age":30,"city":"Paris"}

Common Pitfalls

Common mistakes include passing a non-iterable or an iterable with items that are not two-element arrays. Also, keys must be strings or symbols; other types will be converted to strings.

Wrong usage example:

const wrong = Object.fromEntries(["name", "Alice"]); // Throws error

Correct usage:

const correct = Object.fromEntries([['name', 'Alice']]);

Quick Reference

Feature	Description
Input	Iterable of [key, value] pairs (e.g., array of arrays)
Output	New object with keys and values from input
Key Types	Strings or symbols (others converted to strings)
Throws Error	If input is not iterable or pairs are not length 2
Use Case	Convert Map or array of pairs to object

Key Takeaways

Object.fromEntries converts arrays of key-value pairs into objects.

Input must be an iterable of two-element arrays representing [key, value].

Keys are converted to strings if they are not strings or symbols.

Passing invalid input causes errors, so ensure correct structure.

Useful to transform Maps or arrays back into plain objects.