difference between let, const and var in javascript code example

Example 1: Difference between let and var in javascript

let a = 'hello'; // globally scoped
var b = 'world'; // globally scoped
console.log(window.a); // undefined
console.log(window.b); // 'world'
var a = 'hello';
var a = 'world'; // No problem, 'hello' is replaced.
let b = 'hello';
let b = 'world'; // SyntaxError: Identifier 'b' has already been declared

Example 2: what is the difference between let and const in javascript

The difference is that with const you can only only assign a value to a variable
once, but with let it allows you to reassign after it has been assigned.