JavaScript let

JavaScript let is a keyword used to declare a variable in a block scope. It is a new feature in ES6 (ECMAScript 6) that allows you to create a variable with a limited scope, which is especially useful when working with loops, switch statements, and other control structures.

Why should you use it?

It helps to prevent variable name collisions in your code.
It allows you to create variables with limited scope, making your code more readable and easier to debug.
It helps to avoid using global variables, which can lead to unexpected results.

Let

The 'let' keyword is a new way to declare variables in JavaScript. It was introduced in ES6 (ECMAScript 6) and is now supported by all modern browsers. It is similar to the 'var' keyword, but there are some important differences. The main difference between 'let' and 'var' is that 'let' is block scoped, while 'var' is function scoped. This means that a 'let' variable can only be accessed within the block it is declared in, while a 'var' variable can be accessed from anywhere within the function it is declared in. Another difference between 'let' and 'var' is that 'let' variables are not hoisted, while 'var' variables are. This means that a 'let' variable must be declared before it is used, while a 'var' variable can be used before it is declared. Finally, 'let' variables can be reassigned, while 'var' variables cannot. This means that a 'let' variable can be changed after it is declared, while a 'var' variable cannot.

script.js

// Declare a variable using 'let'
let x = 10;

// Print the value of x
console.log(x);

script.js

// Declare a variable using 'var'
var x = 10;

// Print the value of x
console.log(x);

script.js

// Declare a 'let' variable
let x = 10;

// Print the value of x
console.log(x);

// Reassign the value of x
x = 20;

// Print the new value of x
console.log(x);

script.js

// Declare a 'var' variable
var x = 10;

// Print the value of x
console.log(x);

// Reassign the value of x
x = 20;

// Print the new value of x
console.log(x);

script.js

// Declare a 'let' variable
let x = 10;

// Print the value of x
console.log(x);

// Try to access x outside of the block it was declared in
console.log(x);