15. What is the purpose of the let keyword?

Purpose of the let Keyword in JavaScript

The let keyword is used to declare variables in JavaScript with block scope. It was introduced in ES6 (ECMAScript 2015) as an improvement over var.

Key Features of let

1. Block Scope (Limited to {} blocks)

   • Unlike var, let is confined to the block where it is declared.

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   if (true) {
     let x = 10;
   }
   console.log(x); // ReferenceError: x is not defined
   

   ✅ let is not accessible outside the block.

2. No Hoisting (Cannot be used before declaration)

   • let is hoisted, but not initialized, meaning you cannot use it before declaring.

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   console.log(y); // ReferenceError: Cannot access 'y' before initialization
   let y = 5;
   

3. Allows Reassignment (Unlike const)

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   let a = 10;
   a = 20; // ✅ Allowed
   console.log(a); // Output: 20
   

4. Does Not Allow Redeclaration in the Same Scope

   • Unlike var, let does not allow redeclaration within the same scope.

   javascript
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   let z = 5;
   let z = 10; // ❌ SyntaxError: Identifier 'z' has already been declared
   

Difference Between var, let, and const

When to Use let?

✅ When you need a mutable variable (a variable that can change).
✅ When you need block scope to avoid unintended behavior.
✅ When const is too restrictive (you must reassign the value).

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