解决方法
您需要使用以下liabrary：
将代码放在头标中.
<script type="text/JavaScript" src="jsDraw2D.js"></script>
可从here下载
将以下代码复制并粘贴到希望您的圈子出现的位置…
<script type="text/JavaScript">
//Create jsGraphics object
var gr = new jsGraphics(document.getElementById("canvas"));
//Create jsColor object
var col = new jsColor("red");
//Create jsPen object
var pen = new jsPen(col,1);
//Draw a Line between 2 points
var pt1 = new jsPoint(20,30);
var pt2 = new jsPoint(120,230);
gr.drawLine(pen,pt1,pt2);
//Draw filled circle with pt1 as center point and radius 30.
gr.fillCircle(col,30);
//You can also code with inline object instantiation like below
gr.drawLine(pen,new jsPoint(40,10),new jsPoint(70,150));
</script>
您可以从here查看文档
