//app.js
App({
  ajax:function(){
    let that = this;
    wx.request({
      url: 'https://a.com/url.php',
      method: 'GET',
      success: function(e){
        that.data = 123;
      }
    })
  };
})
//content.js
let app = getApp()
Page({
  getData: function(){;
    app.ajax();
    console.log(app.data); //undefined
  }
})

//app.js
App({
  ajax:function(){
    let that = this;
    let promise = new Promise(function(resolve, reject){
      wx.request({
        url: 'https://a.com/url.php',
        method: 'GET',
        success: function(e){
          that.data = 123;
          resolve();
        }
      })
    });
  };
})
//content.js
let app = getApp()
Page({
  getData: function(){;
    app.ajax().then(()=>{
      console.log(app.data); //123
    });
  }
})

//search.js
var app = getApp();
Page({
  confirm: function(e){
    //获取数据，添加到全局
    let val = e.detail.value;
    app.searchWord = val;
    this.jump();
  },
  jump: function(){
    //跳转tabBar
    wx.switchTab({
      url: '../index/index',
    });
  },
});
 
//index.js
var app = getApp();
Page({
  onShow: function(e){
    //获取全局数据
    let val = app.searchWord;
  }
});
//需要传递参数的页面在跳转前将数据添加到app.js里。需要接受参数的页面在onShow方法接受之前添加到app.js的数据。
　　

wx.request({
  url: 'https://a.com/url.php',
  data: {message: 123},
  method: 'POST',
  header: {
    'content-type': 'application/x-www-form-urlencoded'
  },
  success: function(e){
    console.log(e)
  }
});

wx.request({
  url: url,
  method: 'GET',
  dataType: 'txt',
  success: function(e){
    let json = e.data.trim();
    let arr = JSON.parse(json);
  }
});