每隔一秒打印数组里的元素

[Liqiuyue9597]

第一秒输出1，第二秒输出4。。。
a = [1, 4, 5, 7, 9];

//第一种
for (let i in a) {
  setTimeout(() => {
    console.log(a[i]);
  }, i * 1000 + 1000);
}

//第二种
function sleep(time) {
  return new Promise((resolve, reject) => {
    setTimeout(resolve, time);
  });
}

(async function test(arr) {
  for (var i in arr) {
    await sleep(1000);
    console.log(a[i]);
  }
})(a);