Understanding “Prototypes” in JavaScript
Object
In JavaScript, objects are pairs of keys and values. For example, I wanted to describe my name, I could have an object with two keys:
firstName would point to “Erdal” and lastName would point to “Satık”. Keys in a JavaScript object are Strings.
To create new object in JavaScript;
var person = Object.create(null); // this creates an empty objects
Prototypes
JavaScript objects also have one additional attribute: a pointer to another object. We call this pointer the object’s prototype. If you try to look up a key on an object and it is not found, JavaScript will look for it in the prototype. It will follow the “prototype chain” until it sees a
nullvalue. In that case, it returnsundefined
So, shortly about protoypes;
Every JavaScript object has a prototype. The prototype is also an object.
All JavaScript objects inherit their properties and methods from their prototype.
Objects created using an object literal, or with new Object(), inherit from a prototype called Object.prototype.
Objects created with new Date() inherit the Date.prototype.
All JavaScript objects (Date, Array, RegExp, Function, ….) inherit from the Object.prototype.
Creating Prototype
The standard way to create an object prototype is to use an object constructor function:
The constructor function is the prototype for Person objects.
function Person(first, last, age, eyecolor) {
this.firstName = first;
this.lastName = last;
this.age = age;
this.eyeColor = eyecolor;
}
new keyword to create new objects from the same prototype:
var myFather = new Person("John", "Doe", 50, "blue");
var myMother = new Person("Sally", "Rally", 48, "green");
Adding a Property to an Object — Using the prototype Property
myFather.nationality = "Turkish";
Adding a Method to an Object
myFather.name = function () {
return this.firstName + " " + this.lastName;
};
Using the prototype Property
function Person(first, last, age, eyecolor) {
this.firstName = first;
this.lastName = last;
this.age = age;
this.eyeColor = eyecolor;
}
Have fun !