This article provides detailed information on the source code logic and workflow of the WeChat Mini Program front-end. Friends who need it can refer to it.

Reading the front-end code of the WeChat Mini Program really makes my blood boil. The code logic The design is clear at a glance, there is nothing superfluous, it is really simplicity.

Without further ado, let’s analyze the front-end code directly. Personal opinions, there may be some omissions, it is for reference only.

Basic structure of the file:

First look at the entrance app.js, app (obj) registers a small program. Accepts an object parameter, which specifies the life cyclefunction etc. of the applet. Other files can obtain the app instance through the global method getApp(), and then directly call its properties or methods, such as (getApp().globalData)

//app.js
App({
 onLaunch: function () {
  //調(diào)用API從本地緩存中獲取數(shù)據(jù)
  var logs = wx.getStorageSync('logs') || []
  logs.unshift(Date.now())
  wx.setStorageSync('logs', logs)
 },
 getUserInfo:function(cb){
  var that = this
  if(this.globalData.userInfo){
   typeof cb == "function" && cb(this.globalData.userInfo)
  }else{
   //調(diào)用登錄接口
   wx.login({
    success: function () {
     wx.getUserInfo({
      success: function (res) {
       that.globalData.userInfo = res.userInfo
       typeof cb == "function" && cb(that.globalData.userInfo)
      }
     })
    }
   })
  }
 },
 globalData:{
  userInfo:null
 }
})

I Understand that app.js is the entry initialization file and is also where global API expansion is provided. Let’s analyze the several methods and attributes that come with it

onLaunch hook function will be automatically executed once after the mini program initialization is completed, and then in the mini program life cycle If you don't actively call onLaunch, it will not be executed.

var logs = wx.getStorageSync('logs') || [] Get the logs attribute in the local cache. If the value is empty, set logs= [] Similar to localStorage in HTML5

logs.unshift(Date.now()) Add the current login time to In array

wx.setStorageSync('logs', logs) Store data in the local cache because wx is a global object, so you can directly wx.getStorageSync('logs') in other files to obtain local cache data

getUserInfo function, as the name suggests, is to obtain logged-in user information, which is equivalent to this function providing an interface for obtaining user information. Other pages will not be executed unless called. Other pages call this method through getApp().getUserInfo(function(userinfo){console.log(userinfo);}) to obtain user information.

getUserInfo:function(cb){//參數(shù)為cb,類型為函數(shù)
  var that = this
  if(this.globalData.userInfo){//用戶信息不為空
   typeof cb == "function" && cb(this.globalData.userInfo)//如果參數(shù)cb的類型為函數(shù)，那么執(zhí)行cb,獲取用戶信息；
  }else{//如果用戶信息為空，也就是說第一次調(diào)用getUserInfo，會調(diào)用用戶登錄接口。
   wx.login({
    success: function () {
     wx.getUserInfo({
      success: function (res) {
　　　　　　　　 console.log(res)
       that.globalData.userInfo = res.userInfo//把用戶信息賦給globalData，如果再次調(diào)用getUserInfo函數(shù)的時候，不需要調(diào)用登錄接口
       typeof cb == "function" && cb(that.globalData.userInfo)//如果參數(shù)cb類型為函數(shù)，執(zhí)行cb,獲取用戶信息
      }
     })
    }
   })
  }
 }

globalData object is used to store global data and is called elsewhere

Then Briefly analyze the app.json file. The function of this file is to globally configure the WeChat applet, determine the path of the page file, window performance, set the network timeout, set multiple tabs, etc.

The most important is the pages attribute, which is required and is an array. The elements in the array are strings file paths, specifying which pages the mini program consists of. The first item must be the initial page of the mini program.

{
 "pages":[
  "pages/index/index",
  "pages/logs/logs"
 ],
 "window":{
  "backgroundTextStyle":"light",
  "navigationBarBackgroundColor": "#fff",
  "navigationBarTitleText": "WeChat",
  "navigationBarTextStyle":"black"
 }
}

Then take a look at the project index and logs folders. The initial project of the WeChat applet puts the js, wxss, and wxml related to each page in their own files, so that the structure looks much clearer.

Let’s first look at the index folder, which is the initial page of the mini program. Under the index folder are three small files: index.js, index.wxml, and index.wxss. The mini program separates js, css, and html codes and puts them in separate files, each performing its own duties. The js and style sheet file names must be consistent with the wxml file name of the current folder, so as to ensure that the effects of js and style sheets can be displayed on the page. I appreciate this kind of design concept, which is neat and uniform, with clear responsibilities, and reduces the complexity of code design.

　index.wxml, this is a common template file, data-driven, those who have developed front-end mvc, mvvm project will be familiar with this, after all, it is based on # Developed by ##react. ?medicine. page() to register a page. Accepts an OBJECT parameter, which specifies the page's initial data, life cycle functions, event handling functions, etc.

<!--index.wxml-->
<view class="container">//視圖容器
 <view bindtap="bindViewTap" class="userinfo">//bindtap為容器綁定點擊觸摸事件，在觸摸離開時觸發(fā)bindViewTap事件處理函數(shù)，bindViewTap通過index.js page()設(shè)置添加
  <image class="userinfo-avatar" src="{{userInfo.avatarUrl}}" background-size="cover"></image>//大雙括號的變量來自于index.js的data對象解析成對應(yīng)的值，而且是實時的
  <text class="userinfo-nickname">{{userInfo.nickName}}</text>
 </view>
 <view class="usermotto">
  <text class="user-motto">{{motto}}</text>
 </view>
</view>

index.wxss fileOnly renders the current page and will overwrite the same style of global app.wxss.

　 再分析下logs日志文件夾，logs文件夾下為logs.wxml、logs.js、logs.wxss、logs.json，同理保證同名，才能完成效果渲染。

　 logs.wxml文件

<!--logs.wxml-->
<view class="container log-list">
 <block wx:for="{{logs}}" wx:for-item="log">//block容器作用，無其他實際含義。wx:for作用：遍歷logs數(shù)組，遍歷多少次，block塊就會復(fù)制多少次，for-item等同于為<br>遍歷元素起一個變量名，方便引用。<br>
  <text class="log-item">{{index + 1}}. {{log}}</text>
 </block>
</view>

　　logs.js 文件

//logs.js
var util = require('../../utils/util.js') //util.js相當(dāng)于一個函數(shù)庫，我們可以在這個文件內(nèi)自定義擴(kuò)展和封裝一些常用的函數(shù)和方法
Page({
 data: {
  logs: []
 },
 onLoad: function () {
  this.setData({
   logs: (wx.getStorageSync('logs') || []).map(function (log) {//通過wx.getStorageSync獲取本地緩存的logs日志數(shù)據(jù)
    return util.formatTime(new Date(log))//日期格式化
   })
  })
 }
})

　　logs.json文件

{
  "navigationBarTitleText": "查看啟動日志"  //當(dāng)前頁面配置文件，設(shè)置window當(dāng)前頁面頂部導(dǎo)航欄標(biāo)題等相關(guān)內(nèi)容
}
　　

基本頁面結(jié)構(gòu)和邏輯就這么簡單，暴露給我們的沒有一點令人費解的東西。

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