​x
 
<!DOCTYPE html>
<html>
<body>
​
<canvas id="myCanvas" width="200" height="200" style="border:1px solid">
Your browser does not support the canvas element.
</canvas>
​
<script type="text/javascript">
var c=document.getElementById("myCanvas");
var cxt=c.getContext("2d");
cxt.fillStyle="#92B901";
cxt.fillRect(50,50,100,100);
function clearCanvas()
{
c.height=c.height;
}
</script>
<br />
<button onclick="clearCanvas()">清空画布</button>
</body>
</html>
​