JS Tutorials
JS Introduction
JS Syntax
JS Comments
JS Variables
JS Operators
JS Data Types
JS Functions
JS Objects
JS Numbers
JS Arrays
JS Array Methods
JS Booleans
JS Events
JS Strings
JS Dates
JS Maths
JS Objects
Object Definition
Object Properties
Object Methods
Object Display
Object Prototypes
Object Iterables
Object Sets
Object Maps
Object References
JS Functions
Function Definition
Function Parameters
Function Invocation
Function Call
Function Apply
Function ClosuresJS Classes
Class Intro
Class Inhertitance
Class Static
JS Async
JS Callbacks
JS Aysnchronous
JS Promises
JS ASync/Await
Previous
JavaScript Object Prototypes
All JavaScript objects inherit properties and methods from a prototype.
In the previous chapter we learned how to use an object constructor:
Example
function Person(first,
last, age, eyecolor) {
this.firstName = first;
this.lastName = last;
this.age = age;
this.eyeColor = eyecolor;
}
const myFather = new Person("John", "Doe", 50, "blue");
const myMother = new Person("Sally", "Rally", 48, "green");
We also learned that you can not add a new property to an existing object constructor:
Example
Person.nationality
= "English";
To add a new property to a constructor, you must add it to the constructor function:
Example
function Person(first,
last, age, eyecolor) {
this.firstName = first;
this.lastName = last;
this.age = age;
this.eyeColor =
eyecolor;
this.nationality = "English";
}
Prototype Inheritance
All JavaScript objects inherit properties and methods from a prototype:
Dateobjects inherit fromDate.prototypeArrayobjects inherit fromArray.prototypePersonobjects inherit fromPerson.prototype
The Object.prototype is on the top of the prototype
inheritance chain:
Date objects, Array
objects, and Person objects inherit from Object.prototype.
Adding Properties and Methods to Objects
Sometimes you want to add new properties (or methods) to all existing objects of a given type.
Sometimes you want to add new properties (or methods) to an object constructor.
Using the prototype Property
The JavaScript prototype property allows you to add new
properties to object
constructors:
Example
function Person(first,
last, age, eyecolor) {
this.firstName = first;
this.lastName = last;
this.age = age;
this.eyeColor = eyecolor;
}
Person.prototype.nationality = "English";
The JavaScript prototype property also allows you to add new
methods to objects
constructors:
Example
function Person(first,
last, age, eyecolor) {
this.firstName = first;
this.lastName = last;
this.age = age;
this.eyeColor = eyecolor;
}
Person.prototype.name = function() {
return
this.firstName + " " + this.lastName;
};