<!DOCTYPE html> <html> <head lang="en"> <meta charset="UTF-8"> <title></title> </head> <body onload="star()"> <canvas id="canvas" width="800" height="500" style="border: 1px #ccc solid;"></canvas> </body> </html>
<script>
function star(){
var canvas=document.getElementById("canvas");
var cxt=canvas.getContext("2d");
cxt.translate(100,100);
var s=50;
cxt.beginPath();
cxt.fillStyle="blue";
var x=Math.sin(0);
var y=Math.cos(0);
var dig=Math.PI/5*4;
for(var i=0;i<5;i++){
var x=Math.sin(i*dig);
var y=Math.cos(i*dig);
cxt.lineTo(x*s,y*s);
}
cxt.closePath();
cxt.fill();
}
</script>
原文：http://www.cnblogs.com/bm20131123/p/5013427.html