一般来说 绘制很多张图片 中间有几张没画出来 通常就是没load得原因，具体如下：

let arr = ['img1','img2','img3'];let Canvas = document.createElement('canvas');ctx = Canvas.getContext("2d");let {W, H} = {100, 200};let scaleBy = 2;arr.forEach(e => {    let bgImg = document.creatElement('img');    bgImg.src = e;    bgImg.onload = () => {        ctx.drawImage(bgImg, 0, 0, W * scaleBy, H * scaleBy);                let newImg = document.createElement('img');        newImg.src = Canvas.toDataURL();        document.body.appendChild(newImg);    }})