How do I make a Javascript class a child of another class

Question

I have the following code and have came across the call and prototype.constructor methods but don't have enough knowledge to make them work properly. Can some one fill in the knowledge I am missing. Here an Administrator is a User.

    function User(user) {
      this.id = user.id;
      this.email = user.email;
      this.firstname = user.firstname;
      this.lastname = user.lastname;
      this.age = user.age;
    }       

    User.prototype.fullName = function(){
        return this.firstname + ' ' + this.lastname
    }

    function Admin(admin){
        this.writer = admin.writer;
        this.editor = admin.editor;
        this.publisher = admin.publisher;
        //User.call(this);
    }

    Admin.prototype.fullAccess = function(){
        return (this.writer && this.editor && this.publisher);
    }

    //Admin.prototype = new User();
    //Admin.prototype.constructor = Admin;

    var user1 = new User({
        'id': 1,
        'email': '[email protected]', 
        'firstname': 'Stephen',
        'lastname': 'Brown',
        'age': 44
    });

    var user2 = new User({
        'id': 2,
        'email': '[email protected]', 
        'firstname': 'John',
        'lastname': 'Doe',
        'age': 25
    });

    var admin1 = new Admin({
        'writer': true,
        'editor': true, 
        'publisher': true,
    });

    var admin2 = new Admin({
        'writer': true,
        'editor': true, 
        'publisher': false,
    });

Reference link

km6zla
– km6zla

2013-05-16 16:57:32 +00:00
Commented May 16, 2013 at 16:57 — km6zla
– km6zla, Commented May 16, 2013 at 16:57

bfavaretto · Accepted Answer · 2013-05-17 03:46:55Z

2

You were almost there, it works with a few simple changes:

Uncomment your commented lines
Change User.call(this); to User.call(this, admin);. This will pass the parameters passed to the Admin constructor ahead to the "super" constructor.
Change Admin.prototype = new User(); to Admin.prototype = new User({}); (pass an empty object, otherwise the User constructor will throw an error for trying to access properties of undefined). Or just use Admin.prototype = Object.create(User.prototype); (polyfill required for IE<=8).

http://jsfiddle.net/P6ADX/

edited May 17, 2013 at 3:46

answered May 16, 2013 at 17:01

bfavaretto

72k18 gold badges118 silver badges162 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

metadings Over a year ago

please check out how I'm eliminating the problem with the need to pass 'defaults' to create a prototype object: metadea.de/V

Stephen Brown Over a year ago

Thats great, its nearly working. Only thing is I'm getting the error - TypeError: admin1.fullAccess is not a function when I try accessing it.

Stephen Brown Over a year ago

Switching the lines around seems to have fixed it....

Admin.prototype = new User({}); Admin.prototype.constructor = Admin; 		 Admin.prototype.fullAccess = function(){   return (this.writer && this.editor && this.publisher); }

bfavaretto Over a year ago

@StephenBrown Glad you figured that out, I'm too late! :-)

bfavaretto Over a year ago

@metadings I didn't have enough time to understand your library in depth, but I'll keep it bookmarked and come back to it later. Looks like you put a lot of effort there - although my personal js coding style is to usually avoid classical inheritance patterns.

Collectives™ on Stack Overflow

How do I make a Javascript class a child of another class

1 Answer 1

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related