Let, Const And Var In JavaScript | JavaScript Tutorial for Beginners in Hindi [Tutorial 4]

Let, Const And Var In JavaScript | JavaScript Tutorial for Beginners in Hindi

In this video, we’ll explore the differences between let, const, and var, focusing on their scope, redeclaration rules, and reassignment behavior. Whether you’re a beginner or looking to refine your skills, this guide will help you understand when and why to use each keyword effectively.


What You’ll Learn:

Scope:

let: Block-scoped, which means variables declared with let are only accessible within the block they’re defined in. This provides more predictable behavior compared to var, especially within loops and conditionals.

const: Also block-scoped, just like let. Variables declared with const are confined to the block they’re defined in, ensuring that their scope is limited to that specific block.

var: Function-scoped, meaning a variable declared with var is accessible throughout the function it’s declared in, even if it's declared inside a block (e.g., within an if statement or loop). This can sometimes lead to unexpected behavior, as var does not respect block boundaries.


Redeclaration:

let: Does not allow redeclaration of the same variable within the same block. This helps prevent accidental overwriting of variables and promotes cleaner code.

const: Also prevents redeclaration within the same block.

var: Allows redeclaration of the same variable within the same function scope.


Reassignment:

var and let: Both allow reassignment of their values. This means you can change the value of a variable declared with var or let throughout its scope.

const: Does not allow reassignment of its value. Once a variable is declared with const, it cannot be reassigned. This is ideal for variables that should remain constant and ensures their value remains unchanged throughout the scope.

When to Use Each:

let: Use let for variables that need to change values and are scoped within a block. It’s a good choice for modern JavaScript development where block-level scoping is beneficial.

const: Use const for variables that should not change once they’re assigned. This is especially useful for constants and ensuring that certain variables remain immutable throughout their scope.

var: Use var if you’re working with legacy codebases or if you specifically need function-scoped variables. However, be cautious of potential issues with variable redeclaration and scope confusion.



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