<!DOCTYPE html>
<html>
<body>
<p>三种不同的线帽：</p>
<canvas id="myCanvas" width="300" height="150" style="border:1px solid #d3d3d3;">
Your browser does not support the HTML5 canvas tag.
</canvas>
<script>
var c=document.getElementById("myCanvas");
var ctx=c.getContext("2d");
ctx.beginPath();
ctx.lineWidth=10;
ctx.lineCap="butt";
ctx.moveTo(20,20);
ctx.lineTo(200,20);
ctx.stroke();
ctx.lineCap="round";
ctx.moveTo(20,40);
ctx.lineTo(200,40);
ctx.lineCap="square";
ctx.moveTo(20,60);
ctx.lineTo(200,60);
</script>
</body>
</html>