异步循环for...of异步循环for...of: 1.每个都有结果之后，才会进行下一次循环 2.常见的foreach,

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<script>
  function muti (n) {
    return new Promise((resolve, reject) => {
      setTimeout(() => {
        resolve(n * n)
      }, 1000);
    })
  }
  const arr = [1, 2, 3]
  // 同步循环，1秒之后同时打印出数组中的数据
  arr.forEach(async (i) => {
    console.log(await muti(i));

  })

  // 异步调用，每个都有结果之后再进行下次循环，即每隔1秒打印出一个数据
  !(async function () {
    for (let i of arr) {
      const res = await muti(i)
      console.log(res);
    }
  })()
</script>

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