关于文件上传wx.uploadFile的用法？

for(var i=0;i<len;i++){          var $path=$files[i].path;          wx.uploadFile({            url:app.globalData.api+"&r=util.uploader.upload&file=file",            filePath:$path,            name:"file",//规定的key值            header: {              "Content-Type": "multipart/form-data"            },            success:function(res){              console.log(JSON.parse(res.data));              console.log(JSON.parse(res.data).files[0].url)              console.log(JSON.parse(res.data).files[0].filename)              successNum++;              console.log(successNum)              arr.push({                url:JSON.parse(res.data).files[0].url,                filename:JSON.parse(res.data).files[0].filename              });              console.log(arr.length);              console.log(arr)              if(arr.length==successNum){                console.log(that.data.id)                o.post("member/cart/addsd",{                  id:that.data.id,//会员id                  files:arr,//文件列表                  title:that.data.id.title,//原产品详情                  gid:that.data.gid,//原产品id                },function(res){                  console.log(res);                  if(res==1){                    wx.switchTab({                      url:"/pages/member/cart/index"                    });                  }                })                                /*                wx.navigateTo({                  url:"/pages/member/cart/index?id="+that.data.id                })                */              }else{                console.log("没有上传完成")              }            }          })        };d我现在要上传多个文件，但是wx.uploadFile  api只能上传一个文件，于是我便用了循环上传写法，但是实际操作中，比如上传两张图片，第一张图片会自动多上传一次 咋处理