Rediscovering JavaScript

const

The const keyword is used to define a variable whose value shouldn’t change. If you intend to modify the value in a variable, then define it using let; otherwise, define it using const.

Here’s an example that shows the difference between using let and const:

variables/letconst.js

//BROKEN CODE
'use strict';
let price = 120.25;
const tax = 0.825;

price = 110.12;

tax = 1.25;

There’s no issue changing the value of the price variable. However, since tax is defined as a constant, we will get a runtime error when we try to modify the value:

tax = 1.25;
    ^

TypeError: Assignment to constant variable.

Reach of const

Before we declare const as one of the most awesome features in modern JavaScript, let’s understand its limitations. ...