What is a Key in JavaScript?

In this post, we’ll be discussing what a key is in JavaScript and how you can use it to access object properties.

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In JavaScript, a key is a property of an object. A key’s value can be a primitive data type (string, number, boolean, etc.), an array, or even another object. In order to access a key’s value, you must use square brackets notation.

For example, let’s say we have an object called “user” that looks like this:

var user = {
name: “John”,
age: 30,
isAdmin: true

To access the value of the “name” key, we would do the following:

console.log(user[“name”]); // John

If we wanted to access the value of the “age” key, we would do this:

console.log(user[“age”]); // 30

What is a key in JavaScript?

Keys are very important in JavaScript. They are used to access object properties, create arrays, and so much more. In this article, we will talk about what keys are, how they work, and some of the different uses for them.


In JavaScript, a key is a property of an object. A property is a case-sensitive string that represents the name of a value. Keys can be used to index objects and give you quick access to their values.


A key is a string value that represents a property name. A key must be unique within an object. You can use a key to access the value of a property:

// or

A key can also be used to access the value of a computed property:

function getKey(obj, key) {
return obj[key];


In JavaScript, a key is a value used to identify a specific object within a set of objects. A key can be any string or integer value, including an array index.

When you create an associative array ( an object in which each property has a name ), each property is automatically assigned a key. You can also specify your own keys when you create an array:

var myArray = [];
myArray[“firstName”] = “John”;
myArray[“lastName”] = “Doe”;
myArray[“age”] = 46;
myArray[“address”] = “123 Main Street”;

The above array would have the following keys: “firstName”, “lastName”, “age”, and “address”.

You can access the values in an array by using the key as an index, like this:

var firstName = myArray[“firstName”]; // returns “John”

If you use a non-existent key, the result will be undefined:

var middleInitial = myArray[“middleInitial”]; // returns undefined


A key is a value used to identify a specific element in an array or object. In JavaScript, keys are used to access object properties and array elements. They are like variables, but instead of storing a value, they point to another value. Keys can be any data type, including numbers, strings, and symbols.

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