wx.request({
 url: 'test.php', //仅为示例，并非真实的接口地址
 data: {
 x: '',
 y: ''
 },
 header: {
 'content-type': 'application/json' // 默认值
 },
 success (res) {
 console.log(res.data)
 }
})

class Axios {
 constructor() {
  this.instance = null // 类的实例
  this.config = defaultConfig
 }

 create(instanceConfig) {
  const { config } = this
  // 创建实例的时候添加基本配置
  this.config = {
   ...config,
   ...instanceConfig
  }
  return this
 }

 // 单例
 static getInstance() {
  if (!this.instance) {
    this.instance = new Axios()
  }
  return this.instance
 }
}

const axios = Axios.getInstance()

const dispatchRequest = function(config) {
 return new Promise((resolve, reject) => {
  wx.request({
   ...config,
   url: config.base + config.url,
   success: res => {
    resolve(res)
   },
   fail: res => {
    reject(res)
   }
  })
 })
}

request(options) {
 const { config } = this
 // 实例请求的时候添加基本配置
 const requsetOptions = {
  ...config,
  ...options
 }
 return dispatchRequest(requsetOptions)
}

const instance = (config = {}) => {
 return axios.create({
  base: globalApi,
  ...config
 })
}

export function request(options) {
 const { baseConfig, url, method, data, isLogin } = options
 instance(baseConfig)
  .request({
   url,
   method: method || 'GET',
   data
  })
  .then(res => {
   options.success && options.success(res)
  })
  .catch(err => {
   if (options.error) {
    options.error(err)
   } else {
    errAlert()
   }
  })
 }
}

class InterceptorManager {
 constructor() {
  this.fulfilled = null
  this.rejected = null
 }

 use(fulfilled, rejected) {
  this.fulfilled = fulfilled
  this.rejected = rejected
 }
}

constructor() {
 this.instance = null // 类的实例
 this.config = defaultConfig
 this.interceptors = {
  request: new InterceptorManager(),
  response: new InterceptorManager()
 }
}

request(options) {
  const { config, interceptors } = this
  // 实例请求的时候添加基本配置
  const requsetOptions = {
   ...config,
   ...options
  }

  const promiseArr = [] // promise存储队列

  // 请求拦截器
  promiseArr.push({
   fulfilled: interceptors.request.fulfilled,
   rejected: interceptors.request.rejected
  })

  // 请求
  promiseArr.push({
   fulfilled: dispatchRequest,
   rejected: null
  })

  // 回调拦截器
  promiseArr.push({
   fulfilled: interceptors.response.fulfilled,
   rejected: interceptors.response.rejected
  })

  let p = Promise.resolve(requsetOptions)
  promiseArr.forEach(ele => {
   p = p.then(ele['fulfilled'], ele['rejected'])
  })

  return p
 }

axios.interceptors.request.use(
 request => {
  return request
 },
 err => {
  console.error(err)
 }
)

axios.interceptors.response.use(
 response => {
  return response
 },
 err => {
  console.error(err)
 }
)