var url = "https://avuejs.com/images/logo-bg.jpg";
this.downFile(url,'logo.jpg');

downFile (url, saveName) {
   if (typeof url == 'object' && url instanceof Blob) {
       url = URL.createObjectURL(url); // 创建blob地址
   }
   var aLink = document.createElement('a');
   aLink.href = url;
   aLink.download = saveName || ''; // HTML5新增的属性，指定保存文件名，可以不要后缀，注意，file:///模式下不会生效
   var event;
   if (window.MouseEvent) {
       event = new MouseEvent('click');
   } else {
       event = document.createEvent('MouseEvents');
       event.initMouseEvent('click', true, false, window, 0, 0, 0, 0, 0, false,
           false, false, false, 0, null);
   }
   aLink.dispatchEvent(event);
}