微信小程序处理pages的函数比app.js先执行

  weappLogin() {
    return new Promise((resolve, reject) => {
      wx.checkSession({
        success: (res) => {
        //成功直接返回
          resolve(res)
        },
        //失败调用wx.login
        fail: () => {
          wx.login({
            success: (res) => {
              wxRequest(this.data.baseUrl, {
                key: this.data.baseKey,
                type: "UserLogin",
                data: {
                  wx_code: res.code,
                }
              }, "POST").then(res => {
                if (res.data.status == 1) {
                  var user = res.data.data.userinfo
                  //存储你后台接口的参数
                  wx.setStorageSync('sign', user.sign)
                  resolve(res)
                }
              })
            }
          })
        },
      })
    })
  },

const app = getApp()
  onLoad: function (options) {
      app.weappLogin().then(res => {
      //执行你的方法
      }
    })
  },