JavaScript实现并发控制且指定并发上限为concurrency

前言：使用Typescript编写如下函数功能 并发控制函数 要求控制任务执行的并发上限为concurrency

/*
 * @Author: wztlink1013
 * @Date: 2022-07-25 19:57:09
 * @LastEditTime: 2022-07-25 19:57:22
 * @Description:
 */
// Practice 1
const test_1 = () => {
  return new Promise(resolve => {
    setTimeout(() => {
      console.log('2000')
      let myDate = new Date()
      console.log('---- ', myDate.toTimeString().substring(0, 8), ' ----')
      resolve(2000)
    }, 2000)
  })
}
const test_2 = () => {
  return new Promise(resolve => {
    setTimeout(() => {
      console.log('3000')
      let myDate = new Date()
      console.log('---- ', myDate.toTimeString().substring(0, 8), ' ----')
      resolve(3000)
    }, 3000)
  })
}
const test_3 = () => {
  return new Promise(resolve => {
    setTimeout(() => {
      console.log('4000')
      let myDate = new Date()
      console.log('---- ', myDate.toTimeString().substring(0, 8), ' ----')
      resolve(4000)
    }, 4000)
  })
}

let arr = [test_1, test_2, test_3]

async function parallel(
  tasks: (() => void)[],
  concurrency: number
): Promise<void> {
  const ret: any[] = []
  const executing: any[] = []

  let myDate = new Date()
  console.log('----start ', myDate.toTimeString().substring(0, 8), ' ----')

  for (const item of tasks) {
    const p = Promise.resolve().then(item)
    ret.push(p)

    if (concurrency <= tasks.length) {
      const e: any = p.then(() => executing.splice(executing.indexOf(e), 1))
      executing.push(e)
      if (executing.length >= concurrency) {
        await Promise.race(executing)
      }
    }
  }
  // return Promise.all(ret);
}
parallel(arr, 2)

参考：

• JavaScript 中如何实现并发控制？ - 掘金