omp-wx/pages/welcome/welcome.js

const APP = getApp();
Page({
  /**
   * 生命周期函数--监听页面加载
   */
  onLoad: function (options) {
    this.login();
  },
  /**
   * 登录
   */
  login: function () {
    wx.login({
      success: res => {
        const params = {
          code: res.code
        }
        //登录
        APP.Post(APP.Url.login, params).then(res => {
          APP.globalData.openId = res.data.userId;
          APP.globalData.openNum = res.data.openNum;
        })
        wx.switchTab({
          url: '/pages/index/index',
        })
      }
    })
  }

})