Invoke your function even before declaring it: Hoisting in JavaScript

Take a Look

Example:

add(2, 6); // 8

function add(x,y){
  return x+y;
}

• We called the add function even before declaring it. This is possible in JavaScript because of Hoisting feature.
• In hoisting, all the declarations are moved to the top of the current scope.
• It is not only applicable to functions but to any other variables.
• We can use any variable even before declaring it. For example:

num1 = 2;
console.log(num1); // 2
var num1;

Hoisting in Action

num1 = 2;
num2 = 6;
add(num1, num2); // 8
var num1;
var num2;
function add(x,y){
  return x+y;
}

let and const

num1 = 2;
console.log(num1); // ReferenceError: Cannot access 'num1' before initialization
let num1;

• With let and const, we cannot use the variable before its declaration. If we try to use, we get RefrenceError as above.
• This is because of hoisting in which the variables declared with let and const are moved to the top and are only declared but not initialized and hence ReferenceError.