console 命令行工具 X clear

console

<canvas id="canvas" height="100" width="300"></canvas>

<script>
	window.onload = function() {
        var canvas = document.getElementById("canvas");
        var ctx = canvas.getContext("2d");
        ctx.fillStyle = "green";
        ctx.fillRect(0, 0, 300, 300)
    }

</script>