html5-canvas Animation Animate at a specified interval (add a new rectangle every 1 second)
Example
This example adds a new rectangle to the canvas every 1 second (== a 1 second interval)
Annotated Code:
<!doctype html>
<html>
<head>
<style>
body{ background-color:white; }
#canvas{border:1px solid red; }
</style>
<script>
window.onload=(function(){
// canvas related variables
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
var cw=canvas.width;
var ch=canvas.height;
// animation interval variables
var nextTime=0; // the next animation begins at "nextTime"
var duration=1000; // run animation every 1000ms
var x=20; // the X where the next rect is drawn
// start the animation
requestAnimationFrame(animate);
function animate(currentTime){
// wait for nextTime to occur
if(currentTime<nextTime){
// request another loop of animation
requestAnimationFrame(animate);
// time hasn't elapsed so just return
return;
}
// set nextTime
nextTime=currentTime+duration;
// add another rectangle every 1000ms
ctx.fillStyle='#'+Math.floor(Math.random()*16777215).toString(16);
ctx.fillRect(x,30,30,30);
// update X position for next rectangle
x+=30;
// request another loop of animation
requestAnimationFrame(animate);
}
}); // end $(function(){});
</script>
</head>
<body>
<canvas id="canvas" width=512 height=512></canvas>
</body>
</html>
