异步任务并发量

2023-03-21 15:00:37

现在有下面的代码 实现一个可以控制异步任务并发执行的函数 asyncPool

async function asyncPool({ limit, items }) {
  // write your code
}

async function sleep(n, name = 'test') {
  return new Promise(resolve => {
    console.log(n, name, 'start')
    setTimeout(() => {
      console.log(n, name, 'end', '-----------')
      resolve({ n, name })
    }, n * 1000)
  })
}

async function start() {
  await asyncPool({
    limit: 2,
    items: [
      () => sleep(1, '吃饭'),
      () => sleep(3, '睡觉'),
      () => sleep(5, '写代码'),
      () => sleep(3.5, '打游戏'),
      () => sleep(4, '学习')
    ]
  })
  console.log('all end')
}
start()

输入了五个异步任务 同时只能执行两个 且每个异步任务的时间都不同

async function asyncPool({ limit, items }) {
  const promises = []
  const pool = new Set()

  for (const item of items) {
    const fn = async item => await item()
    const promise = fn(item)
    promises.push(promise)
    pool.add(promise)
    const clean = () => pool.delete(promise)
    promise.then(clean, clean)
    if (pool.size >= limit) {
      await Promise.race(pool)
    }
    // Promise. race
  }
  return Promise.all(promises)
}