A **JavaScript prototype** is used to add new properties and methods to an existing *object constructor*. 

An object constructor is made in JavaScript as follows:

function Player(firstName, lastName, team, position) {
  this.firstName = firstName;  
  this.lastName = lastName;
  this.team = team;
  this.position = position;
}

The object can then be assigned values as follows:

var player1 = new Player("Diego", "Maradona", "Argentina", "Forward");
var player2 = new Player("Alan", "Shearer", "England", "Forward");


​Now, if you wanted to add a new property to the `Player` object, JavaScript's prototype property will be needed. This way, the property added will be shared among all instances of the object.

All JavaScript objects inherit properties and methods from a prototype:

- `Date` objects inherit from `Date.prototype`.
- `Array` objects inherit from `Array.prototype`.
- `Player` objects (from the example above) inherit from `Player.prototype`.

The `Object.prototype` is on top of the prototype inheritance chain; ​ `Date` objects, `Array` objects, and `Player` objects all inherit from `Object.prototype`.



Now, if you wanted to add a new property to the `Player` object (for example, the player's age), JavaScript's prototype property will be needed.

All JavaScript objects inherit properties and methods from a prototype:

- `Date` objects inherit from `Date.prototype`.
- `Array` objects inherit from `Array.prototype`.
- `Player` objects (from the example above) inherit from `Player.prototype`.

The `Object.prototype` is on the top of the prototype inheritance chain: `Date` objects, `Array` objects, and `Player` objects inherit from `Object.prototype`.



# Code
The following code snippet highlights the syntax needed to use prototypes to add a new "sport" property to the `Player` object:

function Player(firstName, lastName, team, position) {
  this.firstName = firstName;  
  this.lastName = lastName;
  this.team = team;
  this.position = position;
}
var player1 = new Player("Diego", "Maradona", "Argentina", "Forward");
Player.prototype.sport = "Football";
console.log(player1.lastName + " was good at " + player1.sport);

New methods can also be added to the object constructor using `prototype`, as shown below:

function Player(firstName, lastName, team, position) {
  this.firstName = firstName;  
  this.lastName = lastName;
  this.team = team;
  this.position = position;
}
var player1 = new Player("Diego", "Maradona", "Argentina", "Forward");
Player.prototype.showName = function() {
  return this.firstName + " " + this.lastName;
};
console.log(player1.showName());

What is a JavaScript prototype?

A JavaScript prototype is used to add new properties and methods to an existing object constructor. An object constructor is made in JavaScript as follows: 