How to make multiple API calls with a delay between each in Node.js

Question

My goal was to make multiple api calls for a list of data. Lets say I had the following code

const  axios = require('axios');

const  axiosRequests = [];
const strings = ['a', 'b', 'c'];
for (let  str  of  strings) {
    axiosRequests.push(axios.get(`https://www.apiexample.com/get/?cfg=json&value=${str}`))
}

The easiest solutions was to apply the following:

let  responseArray;
try {
    responseArray = await  Promise.all(axiosRequests);
} catch (err) {
    console.log(err);
}

responseArray.map(response  => {
    //make something with the response
{

But the problem I encountered with from the API was the HTTP 429 Too Many Requests response status code, which means that the API restricts the number of requests for a period of time.

I want to add a delay between each request.

How can I do this?

Answer 1

You can call in series. However, I recommend using chunks, to make it more useful.

Using chunk, best performance:

const delay = (ms = 1000) => new Promise((r) => setTimeout(r, ms));

const getInChunk = async function (items, chunkSize) {
  let results = [];
  let chunkPromises = [];
  let chunkResults = [];
  for (let index = 0; index < items.length; index++) {
    if (index % chunkPromises === 0) {
      chunkPromises = [];
      chunkResults.push(await Promise.all(chunkPromises));
    } else {
      chunkPromises.push(
        axios.get(`https://jsonplaceholder.typicode.com/todos/${items[index]}`).then(res => res.data)
      );
    }
  }
  // last chunk
  if (chunkPromises.length) {
    chunkResults.push(await Promise.all(chunkPromises));
  }
  // flatten 
  chunkResults.forEach(chunk =>{
    results = results.concat(chunk)
  })
  console.log(results)
  return results;
};

async function main() {
  const strings = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
  const results = await getInChunk(strings, 5);
  console.log(results);
}
main();

<script src="https://cdnjs.cloudflare.com/ajax/libs/axios/0.19.2/axios.min.js"></script>

Simple:

const axios = require("axios");
const delay = (ms = 1000) => new Promise((r) => setTimeout(r, ms));
const getInSeries = async (promises) => {
  let results = [];
  for (let promise of promises) {
    results.push(await delay().then(() => promise));
  }
  return results;
};
const getInParallel = async (promises) => Promise.all(promises);
async function main() {
  const strings = [1, 2, 3, 4];
  const promises = strings.map((id) =>
    axios
      .get(`https://jsonplaceholder.typicode.com/todos/${id}`)
      .then((res) => res.data)
  );
  const results = await getInSeries(promises);
  console.log(results);
}
main();

<script src="https://cdnjs.cloudflare.com/ajax/libs/axios/0.19.2/axios.min.js"></script>

Performance friendly series. loop one time O(N).

const delay = (ms = 1000) => new Promise((r) => setTimeout(r, ms));
const getTodosSeries = async function (items) {
  let results = [];
  for (let index = 0; index < items.length; index++) {
    await delay();
    const res = await axios.get(
      `https://jsonplaceholder.typicode.com/todos/${items[index]}`
    );
    results.push(res.data);
  }
  return results;
};

async function main() {
  const strings = [1, 2, 3, 4];
  const results = await getTodosSeries(strings);
  console.log(results);
}
main();

<script src="https://cdnjs.cloudflare.com/ajax/libs/axios/0.19.2/axios.min.js"></script>