CODEWITHSUNDEEP
javascriptnode.jsasynchronous
cubefox
cubefox

Reputation: 1301

returning mapped array from chained promises

    function createDataSet(username, region, champion, amount) {

  var dataArray = []; //what I want to return, if possible with .map()

  return getUserId(username, region) //required for getUserMatchlist()
    .then(userId => {
      getUserMatchlist(userId, region, champion, amount); //returns an array of objects
    })
    .then(matchlist => {
      matchlist.forEach(match => {
        getMatchDetails(match.gameId.toString(), region) //uses the Id from the matchlist objects to make another api request for each object
          .then(res => {
            dataArray.push(res); //every res is also an object fetched individually from the api. 
            // I would like to return an array with all the res objects in the order they appear in
          })
          .catch(err => console.log(err));
      });
    });
}

I'm trying to send data that I fetched from multiple apis to my frontend. Fetching the data isn't a problem, however, using .map() didn't work and from what I've read doesn't work well with promises. What is the best way for me to return that object? (function will be executed when a get request is received and dataArray will be sent back)

Upvotes: 0

Views: 28

Answers (1)

Michael Pratt
Michael Pratt

Reputation: 3496

Promise.all(listOfPromises) will resolve to an array containing the resolved result of each promise in listOfPromises.

To apply that to your code, you would want something like (pseudocode):

Promise.all(matchlist.map(match => getMatchDetails(...)))
    .then(listOfMatchDetails => {
        // do stuff with your list!
    });

Upvotes: 2

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