/**

  * 下载文件 - 带进度监控

  * @param url: 文件请求路径

  * @param params: 请求参数

  * @param name: 保存的文件名

  * @param progress: 进度处理回调函数

  * @param success: 下载完成回调函数

  * eg: progressDownLoad({url:'http://loacalhost:8080/downLoad.action',name:'file.rar',progress:function(evt){

  *        console.log(evt);

  *     }});

  **/

  function progressDownLoad({url,filename,params,progress,success}){

      var xhr = new XMLHttpRequest();

      xhr.open("POST", url, true);

      //监听进度事件

      xhr.addEventListener("progress", function (evt) {

          if(progress) try{ progress.call(evt); }catch(e){}

      }, false);

      xhr.responseType = "blob";

      xhr.setRequestHeader("Content-Type","application/x-www-form-urlencoded; charset=UTF-8");

      xhr.onreadystatechange = function () {

          if (xhr.readyState === 4 && xhr.status === 200) {

              if (typeof window.chrome !== 'undefined') {

                  // Chrome version

                  var link = document.createElement('a');

                  link.href = window.URL.createObjectURL(xhr.response);

                  link.download = filename;

                  link.click();

              } else if (typeof window.navigator.msSaveBlob !== 'undefined') {

                  // IE version

                  var blob = new Blob([xhr.response], { type: 'application/force-download' });

                  window.navigator.msSaveBlob(blob, filename);

              } else {

                  // Firefox version

                  var file = new File([xhr.response], filename, { type: 'application/force-download' });

                  window.open(URL.createObjectURL(file));

              }

              if(success) try{ success.call(xhr); }catch(e){}

          }

      };

      // FormData

      //var formData = new FormData();

      var paramsStr = '';

      if(params) for (var key in params) paramsStr += '&'+key+'='+params[key];

      if(paramsStr) paramsStr = paramsStr.substring(1);

      xhr.send(paramsStr);

  }