HTML 元素用于:

//HTML
<canvas id="canv"></canvas>

//Javascript
var canvas = document.getElementById("canv");
canvas.width = canvas.height = 100;
var ctx = canvas.getContext("2d");
ctx.fillStyle = "red";
ctx.fillRect(10, 10, 80, 80);

draw graphics 
The HTML <canvas> element is used to draw graphics, on the fly, via JavaScript. The <canvas> element is only a container for graphics. You must use JavaScript to actually draw the graphics. Canvas has several methods for drawing paths, boxes, circles, text, and adding images.