nodejs 8 setTimeout（）中回调函数的作用域

Question

我正在使用nodejs 8和类功能，但发现此绑定是意外的。

在我下面的代码中，应该在setTimeout创建的闭包中访问xxx变量，但不能访问。 为什么？

class Wechat {

  constructor(option) {
    this.option = option


  }

  verifySource() {
    console.log('verify source...')
  }

  async setMenu() {
    console.log('setMenu...')
    let thisObject = this
    let nick = 'nick xu'
    var xxxx = 'xxxx nick xu'
    let accessToken = await this.getAccessToken()
    console.log('accessToken:', accessToken)
    setTimeout( function() {
      // let abc = await thisObject.getAccessToken()
      // no access to xxxx and nick variables
      // this point to Timeout object
      console.log('2nd time token:', '000000')
    }, 5000 )
    return Promise.resolve(33)
  }




  async getAccessToken() {
    /*
    this.access_token = 'kkkkkk'
    this.expires_in = 7200
    this.access_token_receive_time = 123456
    */
    const timeBuffer = 60 * 10 * 1000 // 10 min
    if (this.access_token && this.expires_in && this.access_token_receive_time) {
      // if any of the above data exist
      // check expire
      let currentTime = new Date().getTime() 
      if (currentTime - this.access_token_receive_time > timeBuffer + this.expires_in * 1000) {
        // token is valid

        return this.access_token
      }
    }

    let result = await rp.get(config.baseUrl + '/token?' + 
      'grant_type=client_credential&appid=' + config.appID +
      '&secret=' + config.appSecret)
    let resultJson = JSON.parse(result)
    console.log('result of token request:', result)
    this.access_token = resultJson.access_token
    this.expires_in = resultJson.expires_in
    this.access_token_receive_time = new Date().getTime()
    return this.access_token

  }

  static distance() {
    console.log('static method distance')
  }
}

在setTimeout回调内部进行调试时。

这指向超时。 到底是怎么回事？

检查观察者，xxxx和nick不可用...

Answer 1

如果您只想绑定正确的“这

 setTimeout.call(this, function(){}) //or put whatever scope you want for this 

如果要在settimeout中添加参数，可以使用此

 let thisObject = this let nick = 'nick xu' var xxxx = 'xxxx nick xu' setTimeout (function (thisObject,nick,xxxx) {},1000,thisObject,nick,xxxx);