JavaScript Let

let is one of the keywords introduced in ECMAScript 6 (ES6) for declaring variables in JavaScript.
It differs from the older var keyword in terms of scoping and hoisting.

Here's an overview of let and its usage:

Block Scope: Unlike var, which has function scope or global scope, let has block scope. This means that variables declared with let are only accessible within the block (i.e., within curly braces {}) in which they are defined.

Example

     function example() {
    if (true) {
        let x = 5;
        console.log(x); // Output: 5
    }
    // console.log(x); // Error: x is not defined
}

No Hoisting:

Variables declared with let are not hoisted to the top of their containing block or function. This means that you cannot access a variable before it is declared within the block.

Example

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

Reassignment:

Variables declared with let can be reassigned values just like variables declared with var.

Example

let y = 10;
y = 15;
console.log(y); // Output: 15

Temporal Dead Zone (TDZ):

The temporal dead zone refers to the period between entering the scope and the actual declaration being encountered. During this time, accessing the variable results in a ReferenceError.

Example

console.log(z); // Output: ReferenceError: Cannot access 'z' before initialization
let z = 20;

Use Cases:

Use let when you need block-scoped variables.
Use let when you want to prevent accidental hoisting and make your code more predictable.
Use let when you need to declare variables that may be reassigned.