Q22: What is the difference between let and var - JavaScript Internals (521 Qs)

You can list out the differences in a tabular format

var	let
It has been available from the beginning of JavaScript	Introduced as part of ES6
It has function scope	It has block scope
Variable declaration will be hoisted, initialized as undefined	Hoisted but not initialized
It is possible to re-declare the variable in the same scope	It is not possible to re-declare the variable

Let's take an example to see the difference,

javascript

function userDetails(username) {
  if (username) {
    console.log(salary); // undefined due to hoisting
    console.log(age); // ReferenceError: Cannot access 'age' before initialization
    let age = 30;
    var salary = 10000;
  }
  console.log(salary); //10000 (accessible due to function scope)
  console.log(age); //error: age is not defined(due to block scope)
}
userDetails("John");