How to Use Variable as Key in JavaScript

Objects follow the rule of maintaining a key-value pair, and the key is meant to be irredundant.

To access a value of an object, we either use the dot(.) operator, or we mention the key string within the square brackets ([]).

But when we set a variable for the key, we can also use that according to some regulations.

Use Variable as Key for Objects in JavaScript

We will set a variable varr and enter the key key in this instance. Later we will define an object obj and set the unique key in obj[varr].

var varr = 'key';
var obj = {};
obj[varr] = 42;
console.log(obj.key);
console.log(obj['key']);

The variable varr was set as the key for the object obj. The actual key is the key stored in varr.

But using a variable as a key means adding the variable in the square brackets along with the object.

Output:

If we wish to console out the value, you can see two ways. One is to use the dot operator and mention the key name explicitly.

Secondly, use a square bracket with the object but in a string form as our key is a string type.

But you cannot access the object’s value using the variable where you stored your key name.