Javascript 循环中的异步函数

Question

I have following code with async function download_file(), its working correctly only where runs as single, but in loop, it's not waiting end of iteration. https://pastebin.com/PRgJRn9i

(async () => {

  for (let year of years) {
    for (let month of months) {
        for (let r of day_rng) {
           await download_file(year, month, r);
          }
    }
  }

})();

Answer 1

i am assuming you want each iteration to wait for the download_file function to end, if so then your download_file function should return a Promise that resolved whenever you are done downloading and done writing the contents as per your code, currently its not returning anything so the await before it won't do anything.

Answer 2

Simply add await to make nodejs wait for the result.

await (async () => {

  for (let year of years) {
    for (let month of months) {
        for (let r of day_rng) {
           await download_file(year, month, r);
          }
    }
  }

})();