Prototype in JavaScript

What is Prototype in JavaScript?
How to create prototype in JavaScript?

The prototype is a fundamental concept of JavaScript and its must to known JavaScript developers and all the JavaScript objects have an object and its property called prototype and its used to add and the custom functions and property.

The example looks like,

var employee = function () {
    //This is a constructor  function.
}

//Crate the instance of above constructor  function and assign in a variable
var empInstance = new employee();
empInstance.deportment = "IT";

console.log(empInstance.deportment);//The output of above is IT.
The example with prototype as given below.
var employee = function () { //This is a constructor  function.}

employee.prototype.deportment = "IT";//Now, for every instance employee will have a deportment.

//Crate the instance of above constructor function and assign in a variable
var empInstance = new employee();
empInstance.deportment = "HR";

console.log(empInstance.deportment);//The output of above is HR not IT.