CODEWITHSUNDEEP
javascriptasynchronousasync-awaites6-promise
retro
retro

Reputation: 51

How to access the data from a promise which is an object property

I have the following array of objects

const people = [
  {
id:'John:1:Aries',
exp:40.3,
scores: [4, 4, 5, 6, 4, 6, 5],
futureScores:Promise.resolve([5, 5, 6]),
  },
  {
id:'Jane:2:Pisces',
exp:57.6,
scores: [6, 5, 6, 6, 4, 5, 6],
futureScores:Promise.resolve([4, 5, 6]),
  },
  {
id:'Tom:3:Leo',
exp:30.3,
scores: [4, 4, 5, 5, 6, 6],
futureScores:Promise.resolve([4, 4, 6]),
  },
  {
id:'Amy:4:Sagittarius',
exp:35.0,
scores: [6, 6, 6, 6, 6, 5],
futureScores:Promise.resolve([6, 5, 6]),
  },
];
const extractId = (people) => {
return people.filter((person) => {
    const id = person.id;
    if(id.includes("a")){
      return person;
    }
})

}
const scores = extractId(people);
const avg = (scores) => {
  const getavg = scores.map((el) => el.scores.reduce((a,b) => a +b , 0)/el.scores.length);
  const allavg = getavg.reduce((a, b) => a+b/getavg.length, 0)
return allavg;
  }

I want to access the futureScores property and record the scores in another variable Tried the following

const future = (scores) => {
  const arr = [];
  const fscore = scores.map((el) => {
      
     const fscores = el.futureScores;
    const result = fscores.then(function(value){
      
      console.log(value);
      arr.concat.value;
    });
    return  result
  })
  
  return fscore;
}
console.log(future(scores));

The first console.log is outputting the scores but console.log(future(scores)) is outputting [ Promise { }, Promise { } ] What am I doing wrong?

Upvotes: 0

Views: 56

Answers (2)

kimobrian254
kimobrian254

Reputation: 577

It's how you're handling promises within a map. The idea is you should return a map of promises and resolve them. Something like this:

const future = (scores) => {
  return scores.map((el) => {
    const fscores = el.futureScores;
    return fscores.then((value) => value);
  })
}

Promise.all(future(scores)).then(res=> {
  console.log(res)
})

The idea is to return fscore which is a single promise but since it's a map, at the end we have an array of promises which we can resolve with Promise.all

I did away with arr.concat.value since you're not using it. And if you want to actually change the array, do arr = arr.concat.value; since concat does not mutate the original array, makes a new one.

Upvotes: 1

nain12
nain12

Reputation: 44

You need to return the array inside of the map function.

const future = (scores) => {
  const arr = [];
  const fscore = scores.map((el) => {
      
    const fscores = el.futureScores;
    const result = fscores.then(function(value){
      
      console.log(value);
       return arr.concat.value;
    });
    return  result
  })
  return fscore;
}
future(scores).forEach( val => {
  console.log(val)
})

Upvotes: 0

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