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?

• Royi Namir: Hero.prototype.MoveHero=function(....)

Answer 1

You can;

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

Answer 2

function Hero()
{
 // add other properties
 this.MoveHero = function( xSpeed, ySpeed )
 {
 this.xPos += xSpeed;
 this.yPos += ySpeed;
 }
}