​x
 
<!DOCTYPE html>
<html>
<body>
<h1>HTML5 Canvas</h1>
​
<canvas id="myCanvas" width="400" height="400" style="border:1px solid">
​
</canvas>
<br>
​
<script>
const c = document.getElementById("myCanvas");
const ctx = c.getContext("2d");
ctx.fillStyle = "#0192B9";
ctx.fillRect(50, 50, 300, 300);
​
function clearCanvas() {
  c.height = 400;
}
</script>
​
<button onclick="clearCanvas()">清空 canvas</button>
​
</body>
</html>
​