How to Set an Object Key Using a Variable in JavaScript

Published Feb 28, 2022  ∙  Updated May 2, 2022

How can we set an object key using a variable in JavaScript?

Suppose we have an object obj.

const obj = {};

Let’s say we want to use the output of uuid() as our key.

import { v4 as uuidv4 } from 'uuid';
const id = uuidv4(); // '9b1deb4d-3b7d-4bad-9bdd-2b0d7b3dcb6d'

We want our object to look like this:

const obj = {
  '9b1deb4d-3b7d-4bad-9bdd-2b0d7b3dcb6d': 0,
  '1b9d6bcd-bbfd-4b2d-9b5d-ab8dfbbd4bed': 0,
}

And not like this:

const obj = {
  id: 0,
}

Use Computed Property Names (bracket notation)

In ES6, we can use Computed Property Names.

const id = uuidv4();
const obj = {
  [id]: 0
};

We can place expressions inside the brackets, and it will be computed and used as the property name.

Add key-value pair after initialization

In ES5, we can simply create the object and then add the key-value pair after initialization.

const id = uuidv4();
const obj = {};
obj[id] = 0;