W3Schools 试用编辑器 - W3Schools 中文教程

<!DOCTYPE html>
<html>
<style>
canvas {
  border: 1px solid grey;
  margin: 5px;
}
</style>

<body>
<h1>HTML5 Canvas</h1>
<h2>The globalCompositeOperation Property</h2>

for (let n = 0; n < gco.length; n++) {
  document.write("<div id='p_" + n + "' style='float:left;'>" + gco[n] + ":<br>");
  const canvas = document.createElement("canvas");
  canvas.width = 120;
  canvas.height = 100;
  document.getElementById("p_" + n).appendChild(canvas);
  const ctx = canvas.getContext("2d");  
  ctx.fillStyle = "blue";
  ctx.fillRect(10, 10, 50, 50);
  ctx.globalCompositeOperation = gco[n];
  ctx.beginPath();
  ctx.fillStyle = "red";
  ctx.arc(50, 50, 30, 0, 2 * Math.PI);
  ctx.fill();
  document.write("</div>");
}</script>

</body>
</html>