unity 数字花炮

window.addEventListener("load", eventWindowLoaded,false);
function eventWindowLoaded(){
canvasApp();
}
function canvasApp(){
var theCanvas=document.getElementById("canvas");
var context=theCanvas.getContext('2d');
counter=0;
var tileSheet = new Image();
tileSheet.addEventListener('load', eventShipLoaded , false);
tileSheet.src = "1.png";
function eventShipLoaded() {
startUp();
}
function drawScreen() {
context.fillStyle = "white";
context.fillRect(0,0,500,500);
context.drawImage(tileSheet,80*counter,288,80,96,0,0,80,96);
counter++;
if (counter>1) {
counter=0;
}
}
function startUp(){
setInterval(drawScreen, 200);
}
}