Prototype

In JavaScript, prototypes are a way to share properties and methods among objects. Every object in JavaScript has a prototype property, which is a reference to another object, called its prototype. When an object is asked for a property that it does not have, its prototype is searched for the property instead.

For example, consider the following code:


function Person(name) {
  this.name = name;
}

Person.prototype.sayHello = function() {
  console.log("Hello, my name is " + this.name);
};

var john = new Person("John");
john.sayHello(); // prints "Hello, my name is John"

In this example, we create a Person constructor function, and add a sayHello method to its prototype. This allows all objects created using the Person constructor to access the sayHello method, even though it is not defined directly on the object. When we create a new Person object using new Person("John"), and call the sayHello method, the output is "Hello, my name is John".