JavaScript let Keyword

The let keyword in JavaScript is used to declare variables that are block-scoped, meaning they are only accessible within the {} block where they are defined. It was introduced in ES6 (ECMAScript 2015) and is now the preferred way to declare variables.

Syntax

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Example: Declaring with let

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Key Features of let

1. Block Scope

let is accessible only within the block ({}) it is defined in.

2. Cannot Be Redeclared in the Same Scope

Unlike var, let variables cannot be redeclared within the same block.

3. Can Be Updated

You can reassign values to a let variable.

4. Not Hoisted Like var

let declarations are hoisted but not initialized. Accessing them before declaration results in a ReferenceError.

5. Best Practice Over var

Always prefer let over var unless you require function-level scoping.

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Key Takeaways

• let allows block-scoped variable declarations.
• It avoids issues like hoisting and accidental redeclaration.
• Use let when a variable’s value will change over time.
• Accessing let before declaration triggers a Temporal Dead Zone error.
• Helps in writing secure, cleaner, and bug-free JavaScript code.