NodeJS: Chain functions automatically in a promise?-CodePudding

I'm currently fetching data from an API and I need to do multiple GET requests (using axios). After all those GET requests are completed, I return a resolved promise.

However, I need to do these GET requests automatically based on an array list:

    function do_api_get_requests() {

        return promise = new Promise(function(resolve, reject) {

          API_IDs = [0, 1, 2];

          axios.get('https://my.api.com/'   API_IDs[0])
          .then(data => {
            // Do something with data

            axios.get('https://my.api.com/'   API_IDs[1])
            .then(data => {
              // Do something with data

              axios.get('https://my.api.com/'   API_IDs[2])
              .then(data => {
                // Do something with data
                
                // Finished, resolve
                resolve("success");
                
              }


            }


          }

        }

    }

This works but the problem is API_IDs isn't always going to be the same array, it will change. So I'm not sure how to chain these requests automatically.

CodePudding user response：

Since you said it may be a variable length array and you show sequencing the requests, you can just loop through the array using async/await:

async function do_api_get_requests(API_IDS) {
    for (let id of API_IDS) {
        const data = await axios.get(`https://my.api.com/${id}`);
        // do something with data here
    }
    return "success";
}

And, since you said the list of API ids would be variable, I made it a parameter that you can pass into the function.

If you wanted to run all the API requests in parallel (which might be OK for a small array, but might be trouble for a large array) and you don't need to run them in a specific order, you can do this:

function do_api_get_requests(API_IDS) {
    return Promise.all(API_IDS.map(async (id) => {
        const data = await axios.get(`https://my.api.com/${id}`);
        // do something with data here for this request
    })).then(() => {
        // make resolved value be "success"
        return "success";
    });
}

Depending upon your circumstances, you could also use Promise.allSettled(). Since you don't show getting results back, it's not clear whether that would be useful or not.

CodePudding user response：

You can use Promise.all() method to do all API requests at the same time, and resolve when all of them resolves.

function do_api_get_requests() {
  const API_IDs = [0, 1, 2];

  let promises = [];
  for (const id of API_IDS) {
    promises.push(axios.get(`https://my.api.com/${id}`));
  }

  return Promise.all(promises);
}

CodePudding user response：

If you use Bluebird.js (a better promise library, and faster than the in-built Promise), you can use Promise.each(), Promise.mapSeries(), or Promisme.reduce() to do what you want.

http://bluebirdjs.com