Understanding the "let" Statement in JavaScript

The keyword "let" in JavaScript declares a block scope local variable. This statement is true. The "let" keyword in JavaScript was introduced as part of the ES6 (ECMAScript 6) specification to declare variables in a different scope compared to the "var" keyword.

Block Scope Local Variable

In JavaScript, a variable declared with "let" is confined to the block, statement, or expression in which it is declared. This type of scope is known as block scope. A block scope variable can be updated but not re-declared within its scope.

For instance, consider the JavaScript code snippet below:

{
    let x = 10;
    if(true){
        let x = 20; // Different variable
        console.log(x); // Outputs 20
    }
    console.log(x); // Outputs 10
}

In this example, there are effectively two separate x variables. The first one is defined in the outer block scope and given the value 10. The second x is defined within the if statement in a separate block scope and given the value 20. Thus, when you log x within the if statement, it outputs 20, reverting to the 'outer' x- which outputs 10 when logged, outside the if block.

Advantages of "let" Statement

Using "let" in JavaScript has several benefits:

1. Prevents Variable Hoisting: Unlike "var" which gets hoisted and can be initialized at any time, "let" variables are not initialized until their definition is evaluated.

2. Catches Common Coding Mistakes: With "let", if you try to use a variable before it's declared, you'll get a ReferenceError. This can be helpful in catching common coding mistakes.

3. Block Scope: "let" helps to control variable leakage, keeping variable scope confined to the block level.

In conclusion, using "let" for declaring variables in your JavaScript could prevent potential bugs and improve code readability. Therefore, it's best to use "let" for block scope local variables, and given its plus points, it is becoming widely adopted in the JavaScript community.