Difference between var, let, const in JavaScript

In JavaScript, one can declare a single variable in three different ways namely var, let and const unlike any other programming language. This can prove a bit confusing to beginners as where to use a particular method.

Previously before the introduction of ES6, var was the only way to write variables in JavaScript. But in ES6 two new ways namely, const and let were introduced to declare and write variables in a modern way. Now one might wonder, Is there any difference between these three techniques or Are they just the same? The answer is , YES they are different in nature as compared to each other. Firstly talking in terms of scope, var is globally scoped while let and const can be defined as block-scoped variables.

For eg. see the code given below

In the above Image, You can see that the variables which are declared with var keyword, will be accessed from anywhere in the code. Whereas, variables declared inside the For loop will not be accessed from outside as they are declared using let and const keyword.

Furthermore, Variables declared with var keyword can be re-declared as well as updated, while variables with “let” keyword can only be updated they can not be re-declared. Last but not the least, the variables with const keyword can neither be re-declared nor be updated. They all are hoisted at the top of their scope, while While var and let can be declared without being initialized, const must be initialized during declaration

Thanks for Reading :)