node.js function returns empty

Question

I'm trying to access array from out of loop but it seems somethings wrong. What did I miss out on? How should i do that?

funcA(){
  return new Promise((resp, rej) => {
    var list = [1,2,3,4,5];
    var array = [];
    list.forEach(i => {
      funcB(i).then(num => {
        array.push(num);
        console.log(array) //=> [1,2,3,4,5]
      })
    });
    console.log(array) //=> []
    resp(array) //=> []
  })
}

funcB(i){
  return new Promise((resp, rej) => { 
    resp(i);
  })
}

Possible duplicate of How do I return the response from an asynchronous call? — str
– str, Commented Dec 18, 2017 at 8:55
funcB is async. So, you need to wait (hint: Promise.all) for the all the promises of funcB and then do resp(array). — Davin Tryon
– Davin Tryon, Commented Dec 18, 2017 at 8:55
Possible duplicate of How to wait for function's promise in JavaScript — Stamos
– Stamos, Commented Dec 18, 2017 at 8:59

Amit Wagner · Accepted Answer · 2017-12-18 09:05:00Z

1

you can do something like this.

function funcA(){

  var list = [1,2,3,4,5];
  return Promise.all( 
    list.map(val => {
      return funcB(val)
    })
  )
   
}

function funcB(i){
  return new Promise((resp, rej) => { 
    resp(i);
  })
}

funcA().then(arr => console.log(arr))

answered Dec 18, 2017 at 9:05

Amit Wagner

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David Vicente · Accepted Answer · 2017-12-18 09:06:33Z

1

As you are calling an asynchronous function into the loop, you need to wait until all the calls are executed to access the array:

funcA(){
  return new Promise((resp, rej) => {
    var list = [1,2,3,4,5];
    var promisesArray = [];
    list.forEach(i => {
      promisesArray.push(funcB(i));
    });
    resp(Promises.all(promisesArray));
  });
}

answered Dec 18, 2017 at 9:06

David Vicente

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