<canvas id="demo" width="600" height="600"></canvas>

<script language="javascript">
var cxt=document.getElementById('demo').getContext("2d");
cxt.beginPath();
cxt.fillStyle="#F00";/*设置填充颜色*/
cxt.fillRect(0,0,200,100);/*绘制一个矩形，前两个参数决定开始位置，后两个分别是矩形的宽和高*/
cxt.beginPath();
cxt.strokeStyle="#000";/*设置边框*/
cxt.lineWidth=3;/*边框的宽度*/
cxt.strokeRect(0,120,200,100);
cxt.beginPath();
cxt.moveTo(0,350);
cxt.lineTo(100,250);
cxt.lineTo(200,300);
cxt.closePath();/*可选步骤，关闭绘制的路径*/
cxt.stroke();
</script>