<html>
<head>
<script type="application/javascript">
function draw() {
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
ctx.fillStyle = "red";
ctx.beginPath();
ctx.moveTo(0, 0);
ctx.lineTo(300, 0);
ctx.lineTo(300, 300);
ctx.lineTo(0, 300);
ctx.lineTo(0, 0);
ctx.moveTo(30, 30);
ctx.lineTo(30, 150);
ctx.lineTo(150, 150);
ctx.lineTo(149, 30);
ctx.lineTo(30, 30);
ctx.fill();
}
</script>
</head>
<body onload="draw()">
<canvas id="canvas" width="300" height="300"></canvas>
</body>
</html>