JavaScript实现指定数量的并发限制的示例代码

const group = (list = [], max = 0) => {
  if (!list.length) {
    return list
  }
  let results = []
  for (let i = 0, len = list.length; i < len; i += max) {
    results.push(list.slice(i, i + max))
  }
  return results
}

const requestHandler = async (
  groupedUrl = [],
  callback = () => { }
) => {
  if (!groupedUrl.length) {
    callback()
    return groupedUrl
  }
  const newGroupedUrl = groupedUrl.map(fn => fn())
  const resultsMapper = (results) => results.map(callback)
  const data = await Promise.allSettled(newGroupedUrl).then(resultsMapper)
  return data;
}

const sendRequest = async (
  urls = [],
  max = 0,
  callback = () => { }
) => {
  if (!urls.length) {
    return urls
  }
  const groupedUrls = group(urls, max)
  const results = []
  console.log('start !')
  for (let groupedUrl of groupedUrls) {
    try {
      const result = await requestHandler(groupedUrl, callback)
      results.push(result)
      console.log('go')
    } catch { }
  }
  console.log('done !')
  return results
}

const p1 = () => new Promise((resolve, reject) => setTimeout(reject, 1000, 'p1'))
const p2 = () => Promise.resolve(2)
const p3 = () => new Promise((resolve, reject) => setTimeout(resolve, 2000, 'p3'))
const p4 = () => Promise.resolve(4)
const p5 = () => new Promise((resolve, reject) => setTimeout(reject, 2000, 'p5'))
const p6 = () => Promise.resolve(6)
const p7 = () => new Promise((resolve, reject) => setTimeout(resolve, 1000, 'p7'))
const p8 = () => Promise.resolve(8)
const p9 = () => new Promise((resolve, reject) => setTimeout(reject, 1000, 'p9'))
const p10 = () => Promise.resolve(10)
const p11 = () => new Promise((resolve, reject) => setTimeout(resolve, 2000, 'p10'))
const p12 = () => Promise.resolve(12)
const p13 = () => new Promise((resolve, reject) => setTimeout(reject, 1000, 'p11'))
const p14 = () => Promise.resolve(14)

const ps = [p1, p2, p3, p4, p5, p6, p7, p8, p9, p10, p11, p12, p13, p14]
sendRequest(ps, 3, ({reason, value}) => {
  console.log(reason || value)
})