Variable declaration using const in Javascript

Introduction

We use const to create variables that should not change. It helps keep our code safe and clear.

When you want to store a value that should never change, like a fixed number or a name.

When you want to avoid accidentally changing important data in your program.

When you want to make your code easier to understand by showing which values stay the same.

When working with values that represent constants, like configuration settings or math constants.

When you want to improve code reliability by preventing reassignment of variables.

Syntax

Javascript

const variableName = value;

The variable must be assigned a value when declared.

You cannot change the value of a const variable later.

Examples

This creates a constant named pi with the value 3.14.

Javascript

const pi = 3.14;

This creates a constant string variable name with the value "Alice".

Javascript

const name = "Alice";

This creates a constant boolean variable isActive set to true.

Javascript

const isActive = true;

Sample Program

This program creates a constant variable greeting and prints it. It shows that you cannot change the value later.

Javascript

const greeting = "Hello";
console.log(greeting);

// Trying to change the value will cause an error
// greeting = "Hi"; // Uncommenting this line will cause an error

Important Notes

Even though you cannot reassign a const variable, if it holds an object or array, you can still change the contents inside.

Always use const by default, and only use let if you need to change the variable later.

Summary

const creates variables that cannot be reassigned.

It helps keep values safe and your code clear.

Use const for values that should stay the same.