js 图片保存至手机相册

var triggerEvent = "touchstart";  //指定下载方式
    function savePicture(Url) {
        var blob = new Blob([''], { type: 'application/octet-stream' });
        var url = URL.createObjectURL(blob);
        var a = document.createElement('a');
        a.href = Url;
        a.download = Url.replace(/(.*\/)*([^.]+.*)/ig, "$2").split("?")[0];
        var e = document.createEvent('MouseEvents');
        e.initMouseEvent('click', true, false, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null);
        a.dispatchEvent(e);
        URL.revokeObjectURL(url);
    }
savePicture(Url); 
// Url 为图片的服务器地址  http://****.com/cwap/images/userqrcode/06144477550415791.pngfinal.png

var file = files[0];//上传控件选择的文件对象
var url = window.URL.createObjectURL(file);//用此方法有兼容问题
savePicture(Url); 


//下面是兼容方法

//获取图片路径
function getObjectURL (file){
  let url = null ;
  if (window.createObjectURL!=undefined) { // basic
    url = window.createObjectURL(file) ;
  } else if (window.URL!=undefined) { // mozilla(firefox)
    url = window.URL.createObjectURL(file) ;
  } else if (window.webkitURL!=undefined) { // webkit or chrome
    url = window.webkitURL.createObjectURL(file) ;
  }
  return url ;
}