js 跨域下载图片

let fileName =  item.split("/")[item.split("/").length - 1];
let image = new Image();
           image.setAttribute('crossOrigin', 'anonymous');
           image.src = item;
           image.onload = () => {
               let canvas = document.createElement('canvas');
               canvas.width = image.width;
               canvas.height = image.height;
               let ctx = canvas.getContext('2d');
               ctx.drawImage(image, 0, 0, image.width, image.height);
               let ext = image.src.substring(image.src.lastIndexOf('.')+1).toLowerCase();
               let dataURL = canvas.toDataURL('image/' + ext);
               downloadImg(dataURL,fileName)
};
let downloadImg = (href, name) => {
        let eleLink = document.createElement('a');
        eleLink.download = name;
        eleLink.href = href;
        eleLink.click();
        eleLink.remove();
};