javascript - NodeJS 异步函数不暂停

Question

我有一个异步函数，它使用await 调用另一个异步函数，但第一个函数不会等待第二个函数完成。

module.exports.checkNewUser = async(uuid) => {
    const getUserQuery = `MATCH (n:USER {uuid:"${uuid}"}) RETURN n;`
    console.log(getUserQuery)
    console.log('1')
    const result = await this.runCypherQuery(getUserQuery)
    console.log('3')
    console.log('results:')
    console.log(JSON.stringify(result, null, indent))
    if(result !== []) throw new Error('user already exists')
    return
}

const request = require('request')
const uri = 'http://localhost:7474/db/data/transaction/commit'

module.exports.runCypherQuery = async(query) => {
    const headers = { Authorization: 'Basic xxx' }
    const json = {statements: [{statement: query, parameters: {}}]}
    //console.log(json)
    request.post({uri: uri, headers: headers, json: json}, (err, res, body) => {
        if(err) throw new Error(err.message)
        //console.log(body)
        const data = body.results[0].data
        console.log('data:')
        console.log(data)
        console.log('2')
        return data
    })
}

终端输出为:

MATCH (n:USER {uuid:"xxx"}) RETURN n;
1
3
results:
undefined
data:
[]
2

Answer 1

您的runCypherQuery 目前没有返回任何特殊内容。为了await它，您需要显式指定它返回一个Promise，该Promise在请求完成后解析。只是 await 一个 async 函数并不意味着 async 函数在解析之前等待所有异步操作完成。将基于回调的 request 转换为 Promise 并返回该 Promise，以便可以正确进行 await 编辑:

module.exports.runCypherQuery = (query) => {
  const headers = { Authorization: 'Basic xxx' }
  const json = {statements: [{statement: query, parameters: {}}]}
  return new Promise((resolve, reject) => {
    request.post({uri: uri, headers: headers, json: json}, (err, res, body) => {
      if(err) reject(err.message)
      //console.log(body)
      const data = body.results[0].data
      console.log('data:')
      console.log(data)
      console.log('2')
      resolve(data)
    })
  })
}