微信 JS SDK 扫码二维码 api scanQRCode, 不会回调 success 函数，而是直接出二维码里的内容（偶尔）

代码如下:

  $(document).on 'wx_loaded', ->
    $('#reserve_confirm').on 'click', (e) ->
      e.preventDefault()
      wx.scanQRCode
        needResult: 1
        scanType: [ 'qrCode' ]
        success: (res) ->
          result = res.resultStr
          $.ajax({
            url: "#{wx_admin_reserve_confirm_path}"
            type: "POST"
            data: {user_id: result}
            success: () ->
              window.location.href = "#{wx_admin_reserve_buildings_path}?user_id=\#{result}"
          })