js 跨域下载图片解决方法

同源可以直接使用a标签，跨域时神烦，测试成功的代码如下，可直接复制测试

    function ddd(){
        console.log(22222)
        // 创建隐藏的可下载链接  
        // let  blob = 'http://pic.c-ctrip.com/VacationH5Pic/mice/wechat/ewm01.png';
        // var a = document.createElement('a');
        // a.style.display = 'none';
        // a.href = blob;        
        // a.download = 'QRcode.jpg';
        // document.body.appendChild(a);
        // a.click();
        // //移除元素
        // document.body.removeChild(a);
        //canvans下载
        let src = 'http://pic.c-ctrip.com/VacationH5Pic/mice/wechat/ewm01.png';
        var canvas = document.createElement('canvas');
        var img = document.createElement('img');
        img.onload = function(e) {
            canvas.width = img.width;
            canvas.height = img.height;
            var context = canvas.getContext('2d');
            context.drawImage(img, 0, 0, img.width, img.height);
            // window.navigator.msSaveBlob(canvas.msToBlob(),'image.jpg');
            // saveAs(imageDataUrl, '附件');
            canvas.getContext('2d').drawImage(img, 0, 0, img.width, img.height);
            canvas.toBlob((blob)=>{
                let link = document.createElement('a');
                link.href = window.URL.createObjectURL(blob);
                link.download = 'aaa'; 
                link.click();  
            }, "image/jpeg");
            // context.toBlob(function(blob) {
            // console.log('blob :', blob);
            

            // let link = document.createElement('a');
            // link.href = window.URL.createObjectURL(blob);
            // link.download = 'aaa';
            // }, "image/jpeg");
        }
        img.setAttribute("crossOrigin",'Anonymous');
        img.src = src;
    }