问题描述
我希望能够从构造函数中创建Canvas元素，以便我可以创建这样的函数。
I would like to be able to make Canvas elements from the constructor so that I could make a function like this.
function createCanvasContext(height,width)
{
var body = document.getElementsById('body')[0];
var canvas = new Canvas();
canvas.height=height;
canvas.width = width;
var context = canvas.getContext('2d');
body.appendChild(canvas);
return context;
}
我在行var canvas = new Canvas（）说出错了'画布未定义'HTML5不允许从构造函数创建元素吗？或者是否需要传递给构造函数的参数。任何想法都会很棒。
I get an error at the line var canvas = new Canvas() saying that 'Canvas is undefined' does HTML5 not allow creating elements from the constructor? or are there parameters that I need to pass to the constructor. Any ideas would be great.
推荐答案
虽然你可以做 new Image（）就好了，新的Canvas（）不是什么东西！ Canvas 虽然 HTMLCanvasElement 是，但它甚至都不是。尽管如此，你不能使用它的构造函数。
While you can do new Image() just fine, new Canvas() isn't a thing! Canvas Isn't even a thing, though HTMLCanvasElement is. Nonetheless you cannot use its constructor.
document.createElement（'canvas'）; 就是你想要的。你必须使用它，就像使用div一样。
document.createElement('canvas'); is what you want. You have to use that, just like with divs.
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