PianoTime/wechat/pages/index/index.js

var app = getApp()
Page({
  
  onLoad: function () {
    wx.getSystemInfo({
      success: (res) => {
        this.setData({
          screenWidth: res.screenWidth,
          screenHeight: res.screenHeight,
          bannerWidth: res.screenWidth,
          bannerHeight: res.screenWidth * 363 / 543
        })
      }
    })

    var pt_student_id = wx.getStorageSync('pt_student_id')
    if (!pt_student_id) {
      wx.redirectTo({
        url: '/pages/login/index',
      })
    }
  }
})