How to Set an Object Key using a Variable in JavaScript

The beautiful thing about JavaScript is how flexible it is.

One thing you might need to be able to do is set a key of an object using a variable.

This is usually when you don't know the key name until runtime, and therefore cannot hardcode it.

In this post, we'll learn how you can set the key of an object using a variable in JavaScript.

How to set an object key using a variable

To start, let's create an object.

JAVASCRIPT
const object = {};

console.log(object);

BASH
{}

Now let's create a variable to set our new key:

JAVASCRIPT
const key = "key";
const value = "value";

console.log(key);
console.log(value);

BASH
key
value

In the end, we want an object that looks like this:

JAVASCRIPT
{
    key: "value"
}

To do this, you will need to use a computed property name. The syntax for this looks like this:

JAVASCRIPT
const key = "key";
const value = "value";

const object = {
    [key]: value
};

console.log(object);

BASH
{ key: 'value' }

Alternatively, you can also just create an empty object, then assign it the dynamic key-value pair:

JAVASCRIPT
const key = "key";
const value = "value";

const object = {};
object[key] = value;

console.log(object);

BASH
{ key: 'value' }

Conclusion

In this post, we learned how to set an object's key with a dynamic key-value, such as from a variable.

Simply use a computed property name, and you're good to go!

Thanks for reading!

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