Javascript add function to object

Question

Hello there stackoverflow people, I'm messing around with HTML5 and Javascript and I'm trying to add a function to an object in javascript, just like a function is added to a class in C#. Here is my javascript (I know this doesn't work)

function Hero()
{
    this.xPos = 100;
    this.yPos = 100;
    this.image = new Image();
    this.image.src = "Images/Hero.png";
}

function MoveHero( xSpeed, ySpeed )
{
    xPos += xSpeed;
    yPos += ySpeed;
}

Now in my main loop function like so

function main()
{
    canvas.fillStyle = "#555555";
    canvas.fillRect( 0, 0, 500, 500);

    canvas.drawImage( hero.image, hero.xPos, hero.yPos );
    hero.MoveHero(1,1);
}

Now this ofcourse tells me that

"Uncaught TypeError: Object #<Hero> has no method 'MoveHero'"

How would I link the function so I could use

hero.MoveHero(x,y);

If anyone could help me out it would be awesome.

P.S. I am declaring my hero variable globally like so

var hero = new Hero();

is that ok?

Hero.prototype.MoveHero=function(....)

Royi Namir
– Royi Namir

2014-01-21 14:29:59 +00:00
Commented Jan 21, 2014 at 14:29 — Royi Namir
– Royi Namir, Commented Jan 21, 2014 at 14:29

Alex K. · Accepted Answer · 2014-01-21 14:30:11Z

10

You can;

Hero.prototype.MoveHero = function( xSpeed, ySpeed )
{
    this.xPos += xSpeed;
    this.yPos += ySpeed;
}

answered Jan 21, 2014 at 14:30

Alex K.

177k32 gold badges276 silver badges299 bronze badges

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

Comments

Rami Enbashi · Accepted Answer · 2014-01-21 14:38:54Z

1

function Hero()
{
    // add other properties

    this.MoveHero = function( xSpeed, ySpeed )
    {
        this.xPos += xSpeed;
        this.yPos += ySpeed;
    }
}

edited Jan 21, 2014 at 14:38

answered Jan 21, 2014 at 14:33

Rami Enbashi

3,5561 gold badge21 silver badges21 bronze badges

Collectives™ on Stack Overflow

Javascript add function to object

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related