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Javascript – Promises in Asynchronous Loops

I am learning JavaScript and just went over Promises. I tried to write a loop that looked similar to this:

for (let i of someArray) {
   if (condition) {
      await returnsPromise(i)
   }
}

This code does not work, and I was wondering if there is any other syntax that I would have to be aware of.

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2

Answers


  1. 0

    To use await inside a loop, you need to define an async function and then call it within that function.

    async function loop() {
  for (let i of someArray) {
    if (condition) {
      await returnsPromise(i)
    }
  }
}

loop();
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  2. 0

    the await code must still require the async function as a caller. or you can use deno.js then your code will work fine. no need for async function anymore.
    try my code it works fine

    function returnsPromise(ms) {
    return new Promise(resolve => setTimeout(resolve, ms));
}
async function loop(someArray){
  for (let i of someArray) {
    if (true) { // condition
      console.log(await returnsPromise(i), i)
    }
   }
 }
loop([500,1000, 2000])
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