JS学习：测试一下imooc markdown的run代码功能-原创手记-慕课网

发现imooc markdown的代码运行功能，感觉不错。但是貌似没找到使用说明。为了能更好的了解该功能，测试一下：

<!DOCTYPE html>
<html lang="en">
<head>
    <style>
        html,body {margin:0;height:100%;overflow:hidden;}
    </style>
    <meta charset="UTF-8">
    <title>随风而行之青衫磊落险峰行测试imooc的markdown run功能</title>
</head>
<body>
<canvas id="myCanvas" width="800" height="600" style="border: 1px solid black">
    你的浏览器还不支持哦
</canvas>
</body>
<script>
    function drawGrid(backcolor,color, stepx, stepy) {
        context.save()

        context.strokeStyle = color;
        context.fillStyle = backcolor;
        context.lineWidth = 0.5;
        context.fillRect(0, 0, context.canvas.width, context.canvas.height);
        context.globalAlpha = 0.1;

        context.beginPath();
        for (var i = stepx + 0.5; i < context.canvas.width; i += stepx) {
            context.moveTo(i, 0);
            context.lineTo(i, context.canvas.height);
        }
        context.stroke();

        context.beginPath();
        for (var i = stepy + 0.5; i < context.canvas.height; i += stepy) {
            context.moveTo(0, i);
            context.lineTo(context.canvas.width, i);
        }

        context.stroke();

        context.restore();
    }

    var canvas=document.getElementById("myCanvas");
    var context =canvas.getContext('2d');

    drawGrid('black','white',10,10);
</script>
</html>

期待一下是否能在markdown run中正常运行，显示出canvas2d绘制出来的黑色背景网格