# API

Mini program development framework provides rich WeChat native API, can easily tune up WeChat provides capabilities, such as access to user information, local storage, payment functions, etc. Please refer to the API file。

Usually in Mini programs. API There are the following types:

# Event monitoring API

We agreed to, on Beginning API Used to monitor whether an event is triggered, such as:[wx.onSocketOpen ]((wx.onSocketOpen ))，wx.onCompassChange Etc.

this kind API Takes a callback function as an argument, which is called when the event fires, and passes in the relevant data as an argument.

Code Examples

wx.onCompassChange(function (res) {
  console.log(res.direction)
})

# synchronization API

We agreed to, Sync The ending API It's all in sync. API， Such as [wx.setStorageSync ]((wx.setStorageSync ))，wx.getSystemInfoSync Etc. In addition, there are a number of other synchronization API, such as [wx.createWorker ]((wx.createWorker ))，wx.getBackgroundAudioManager Etc., see details API Instructions in the documentation.

synchronization API The result of the execution of the function can be obtained directly through the return value of the function, and an exception will be thrown if the execution fails.

Code Examples

try {
  wx.setStorageSync ('key', 'value')
} catch (e) {
  console.error(e)
}

# asynchronous API

majority API Are asynchronous. API, such as wx.request，wx.login Etc. this kind API The interface usually accepts a Object This parameter supports specifying the following fields on demand to receive the result of the interface call:

Object Dxplaination of parameters

Parameters of the callback function

success，fail，complete A function call is passed in Object Type parameter, containing the following fields:

asynchronous API The results of the implementation need to be obtained through the Object Gets the corresponding callback function passed in a parameter of type. Partially asynchronous API There will also be return values that can be used to implement richer functionality such as wx.request，wx.connectSocket Etc.

Code Examples

wx.login({
  success(res) {
    console.log(res.code)
  }
})

# asynchronous API return Promise

Base library 2.10.2 Version, asynchronous API Support callback & promise Two ways of calling. When the interface parameter Object Object does not contain success/fail/complete Will return by default Promise, otherwise it is still executed by callback, no return value.

# Note

1. Part of the interface such as downloadFile, request, uploadFile, connectSocket, createCamera(small game) itself has a return value, Their promisify Developers need to package themselves.
2. When there is no callback parameter, the asynchronous interface returns promise。If the function call fails to enter fail Logic, Will report error message Uncaught (in promise), the developer can pass catch For the capture.
3. wx.onUnhandledRejection Can listen on the unprocessed Promise Reject the event.

Code Examples

// callback Formal call
wx.chooseImage({
  success(res) {
    console.log('res:', res)
  }
})

// promise Formal call
wx.chooseImage().then(res => console.log('res: ', res))

# Cloud development API

Open and use[WeChat cloud development](https://developers.weixin.qq.com/miniprogram/dev/wxcloud /basis/getting-started.html), you can use the cloud development API, in the Mini Program side directly call the server[Cloud function](https://developers.weixin.qq.com/miniprogram/dev/wxcloud /Guide/functions.html#Cloud function)。

Code Examples

wx.cloud.callFunction({
  // Cloud Function Name 
  name: 'cloudFunc',
  // Parameters passed to the cloud function
  data: {
    a: 1,
    b: 2,
  },
  success: function(res) {
    console.log(res.result) // Example
  },
  fail: console.error
})

// In addition, cloud functions also support promise form calls