Cannonball and Slingshot - The Essential Guide to HTML5 - page 123

Code Explanation

this.sheight = sheight;

… sheight

this.draw = drawAnImage; … draw . This will be the draw method for

objects of this type.

this.moveit = moveball; … This will be the moveit method. Not used.

} Close Picture function

function drawAnImage() {

Header for drawAnImage function

ctx.drawImage(this.img,this.sx,
this.sy,this.swidth,this.sheight);

Draw image using properties of this object

}

Closes function

var target = new Picture(targetx,targety,
targetw,targeth,"hill.jpg");

Construct new Picture object and assign to
target variable

var htarget = new Picture(htargetx,
htargety, htargetw, htargeth, "plateau.jpg");

Construct new Picture object and assign to
htarget variable

var ground = new Myrectangle(0,300,
600,30,"rgb(10,250,0)");

Construct new Myrectangle object and assign
to ground

var cannon = new Myrectangle(cannonx,
cannony,cannonlength,cannonht,"rgb(40,40,0)");

Construct new Myrectangle object and assign
to cannon

var targetindex = everything.length; Save what will be the index for target

everything.push([target,false]);

Add target to everything

everything.push([ground,false]); Add ground to everything

var ballindex = everything.length; Save what will be the index for cball

everything.push([cball,false]);

Add cball to everything

var cannonindex = everything.length;

Save what will be the index for cannon

everything.push([cannon,true,0,
cannonx,cannony+cannonht*.5]);

Add cannon to everything; reserve space for
rotation