how to reload the canvas by external java script?

var c=document.getElementById("c2canvas");
var ctx=c.getContext("2d");
ctx.clearRect(0,0,500,580);

[/code:2dj2fo5h]

I thought maybe clearing the rect may call OnlayourStart function but i am getting null object in my ctx...then somewhere on internet i found this code where it was written it can refresh the canvas from the start.
[code:2dj2fo5h]
var oldcanv = document.getElementById('c2canvas');
document.removeChild(c2canvas)

var canv = document.createElement('c2canvas');
canv.id = 'canvas';
document.body.appendChild(c2canvas);[/code:2dj2fo5h]

but this also did not work , i just need simple way to re-load my whole construct2 canvas by hyperlink ..so the "On start Layout" would get call one time by its trigger whenever someone clicks the hyperlink.