javascript - JS返回不等待等待
问题描述
我正在尝试使用异步等待。
我的应用程序是这样开始的
axios.get(`${ROOT_URL}/ccidxann.php`)
.catch(err => console.error('axios error get', err))
.then(async res => {
const html = res.data
const jobList = await getJobList(html)
console.log(' after each jobList', jobList)
// jsonfile.writeFileSync('jobs.json', jobList, { flag: 'a' })
})
.catch(err => console.error(err))
问题是它jobList
总是作为一个空数组返回。这是getJobList
功能
async function getJobList (html) {
const jobList = []
const dom = new JSDOM(html)
const { window } = dom
const $ = require('jquery')(window)
const jobsInDom = $('table').first().find('td > a')
// AWAIT HERE
await jobsInDom.each(async function (index, jobElem) {
const name = $(jobElem).text()
const url = $(jobElem).attr('href')
// Another AWAIT HERE
const jobDetailsHTML = await getJobDetailsHTML(`${ROOT_URL}/${url}`)
.catch(err => console.error('getJobDetailsHTML err', err))
const domDetails = new JSDOM(jobDetailsHTML)
const { window: windowDetails } = domDetails
const $details = require('jquery')(windowDetails)
const jobDetailsHTMLBody = $details('body').prop('outerHTML')
jobList.push({
_id: url,
name,
detailsHTML: jobDetailsHTMLBody
})
console.log('in each jobList', jobList)
}) //each
return jobList
}
如您所见,我将async
关键字放在了它的前面,
我已经把async
关键字放在回调中each
并放在await
所有异步操作的前面。
的console.log
回调中each
打印填充了值的数组
但似乎return
之前的作品each
即使await
前面有关键字。
而且这里也是getJobDetailsHTML
以防万一。这是一个简单的功能,似乎工作得很好
async function getJobDetailsHTML (url) {
// ANOTHER AWAIT HERE
return await axios.get(url).data
}
解决方案
我认为jobsInDom.each
是同步功能,因此将 await 放在前面不会给您想要的效果。因此,您需要以某种方式获得在所有作业的处理完成时解决的承诺,如下所示:
// handles one element and returns promise
const jobHandler = async jobElem => {
const name = $(jobElem).text()
const url = $(jobElem).attr('href')
const jobDetailsHTML = await getJobDetailsHTML(`${ROOT_URL}/${url}`)
.catch(err => console.error('getJobDetailsHTML err', err))
const domDetails = new JSDOM(jobDetailsHTML)
const { window: windowDetails } = domDetails
const $details = require('jquery')(windowDetails)
const jobDetailsHTMLBody = $details('body').prop('outerHTML')
jobList.push({
_id: url,
name,
detailsHTML: jobDetailsHTMLBody
})
console.log('in each jobList', jobList)
}
const promises = [];
// start processing of each element
jobsInDom.each((index, jobElem) => promises.push(jobHandler(jobElem));
// wait for processing of all job elements
await Promise.all(promises);