CANNONBALL AND SL INGSHOT
Code Explanation
var verticalvel1; Variable to hold vertical displacement at start of interval
var verticalvel2; Variable to hold vertical displacement at end of interval,
after change by gravity
var gravity = 2; Amount of change in vertical displacement. Arbitrary.
Makes for a nice arc.
var iballx = 20; Initial horizontal coordinate for the ball
var ibally = 300; Initial vertical coordinate for the ball
function Ball(sx,sy,rad,stylestring) { Start of function to define a Ball. object. Use the
parameters to set the properties.
this.sx = sx; Set the sx property of THIS object
this.sy = sy; ...sy
this.rad = rad; ...rad
this.draw = drawball; ...draw. Since drawball is the name of a function, this
makes draw a method that can be invoked
this.moveit = moveball; ...moveit set to the function moveball
this.fillstyle = stylestring; ...fillstyle
} Close the Ball function
function drawball() { Header for the drawball function
ctx.fillStyle=this.fillstyle; Set up the fillStyle using the property of this object
ctx.beginPath(); Start a path
ctx.arc(this.sx,this.sy
,this.rad,0,Math.PI*2,true);
Set up to draw a circlectx.fill(); Draw the path as a filled path