App Introduction

Introduction

App() represents top-level applications and manages all pages and global data and provides lifecycle method. It is also a construction method, for generating the App instance.

A Mini Program is an App instance.

Typically, at the root directory of each Mini Program, there are three files.

• app.js: application logic

• app.acss: application style (optional)

• app.json: application configuration

Sample

Here is a simple app.json.

{
  "pages": [
    "pages/index/index",
    "pages/logs/index"
  ],
  "window": {
    "defaultTitle": "Demo"
  }
}

The configuration above indicates that two pages are included in the Mini Program, and the default title is Demo for the application.

A simple app.js code is shown below. It has four life-cycle methods.

App({
  onLaunch(options) {
  	// called when opened
  },
  onShow(options) {
  	// called when opened or come foreground
  },
  onHide() {
  	// called when it goes background
  },
  onError(msg) {
  	// called on JavaScript error or API invoke exception
    console.log(msg)
  },
  // global data
  globalData: {
    foo: true,
  }
})