JS Array Const

ECMAScript 2015 (ES6)

Introduced in 2015, JavaScript brought a significant keyword: const. It’s now a common practice to declare arrays using const.

Example

const cars = [“Saab”, “Volvo”, “BMW”];

Cannot be Reassigned

Once declared with const, an array cannot be reassigned.

Example

const cars = [“Saab”, “Volvo”, “BMW”];
cars = [“Toyota”, “Volvo”, “Audi”]; // ERROR

Arrays are Not Constants

The keyword const might be a bit misleading.

It doesn’t create a constant array; rather, it establishes a constant reference to an array.

Consequently, although you can’t reassign the array itself, you can still modify its elements.

Elements Can be Reassigned

You can modify the elements of a constant array.

Example

// You can create a constant array:
const cars = [“Saab”, “Volvo”, “BMW”];

// You can change an element:
cars[0] = “Toyota”;

// You can add an element:
cars.push(“Audi”);