How to add delay inside async forEach loop

Question

I have a trading script that gets values from "coin" object, which is filled by an API call, then iterates inside async forEach loop, then sends trade orders to the server.

The server requires at least 100 ms between each request. I used setTimeout with promise, but I can see results coming to console all at once so server bans after a while.

How should I design delaying?
js

Object.keys(coin).forEach(async function(key) {
 const coinz = coin[key];
  let line1 = sellcoinCalc("sell", coinz.usdPair, coinz.usdOrder)
  let line2 = buycoinCalc("buy", coinz.usdtPair, line1)          
  let result = line2-line1
 if (result > 0){
  console.log(result)
  }
 if (result >= profit){
      await sellcoinTrade("sell", coinz.usdPair, coinz.usdOrder)
      await buycoinTrade("buy", coinz.usdtPair, line1)            
  }
      await new Promise(r => setTimeout(r, 200));
  });

Does this answer your question? [How do I add a delay in a JavaScript loop?](https://stackoverflow.com/questions/3583724/how-do-i-add-a-delay-in-a-javascript-loop) — Zydnar, Jan 07 '20 at 13:14
Another solution would be using streams like in rxjs library. — Zydnar, Jan 07 '20 at 13:15
In order for this to work the `forEach` callback would have to be `await`ed by the inner workings of forEach. Pretty sure that's not the case. You will have to add the wait part some other way. — James, Jan 07 '20 at 14:04

gazdagergo · Answer 1 · 2020-01-07T14:16:59.990

3

Use for loop instead of forEach and wrap the whole stuff into an async function:

const sleep = ms => new Promise(r => setTimeout(r, ms))

const tradeFn = async () => {
  try {
    for (let i in coin) {
      await sleep(200);
      const coinz = coin[i];
      await sellcoinTrade(coinz /* etc */);
      // etc
    }
  } catch(e) {
    // handle rejections
  }
}

edited Jan 07 '20 at 14:16

answered Jan 07 '20 at 13:31

gazdagergo

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Do i have to use for loop ? , forEach method is simpler for complex coin object – trmt Jan 07 '20 at 13:53
Yes, but do not work asynchronously for some reason. This basic `for` loop or the `for (let i in coin)` solution will work. – gazdagergo Jan 07 '20 at 14:16
1

Alternatively you can use for...await loop but it requires custom iterator function. – Zydnar Jan 07 '20 at 15:31
1

this is work, for me. – Iklan Hits Jun 18 '23 at 07:24

How to add delay inside async forEach loop

1 Answers1