如何在异步 forEach 循环中添加延迟

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));
  });

Answer 1

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
  }
}