The Essential Guide to HTML5

CHAPTER 4

Code Explanation

} Close the function

function moveball(dx,dy) { Header for the moveball function

this.sx +=dx; Increment the sx property by dx

this.sy +=dy; Increment the sy property by dy

} Close function

var cball = new Ball(iballx,ibally,

10,"rgb(250,0,0)");

Create a new Ball object at the indicated position,

radius, and color. Assign it to the variable cball. Note

that nothing is drawn at this time. The information is just

set up for later use.

function Myrectangle(sx,sy,swidth,

sheight,stylestring) {

Header for function to construct a Myrectangle object

this.sx = sx; Sets the sx property of THIS object

this.sy = sy; ...sy

this.swidth = swidth; ...swidth

this.sheight = sheight; ...sheight

this.fillstyle = stylestring; ...stylestring

this.draw = drawrects; ... draw. This sets up a method that can be invoked.

this.moveit = moveball; ....moveit. This sets up a method that can be invoked.
It is not used in this program.

} Close Myrectangle function

function drawrects() { Header for drawrects function

ctx.fillStyle = this.fillstyle; Set the fillStyle

ctx.fillRect(this.sx,this.sy,

this.swidth,this.sheight);

Draw the rectangle using the object properties

} Close function