How do I retrieve all indexes that match condition in JavaScript?

Question

I need to get the indexes of the items in question.options array that have 'correct: true' on them. It only returns the first index (because of findIndex), need to retrieve all indexes that match (for questions with more than one answer). I'll then need to add one to each of the indexes for correctAnswerOptions array to pass to another function. Here's my code.

getCorrectAnswers(question: QuizQuestion) {
  console.log(question.options.findIndex(item => item.correct));
  const identifiedCorrectAnswers = question.options.filter(item => item.correct);
  this.numberOfCorrectOptions = identifiedCorrectAnswers.length;

  // need to push the correct answer option numbers here!
  this.correctAnswers.push(identifiedCorrectAnswers);
  // pass the correct answers
  this.setExplanationAndCorrectAnswerMessages(this.correctAnswers);

  return identifiedCorrectAnswers;
}

check my answer @integral it will directly give you the array of correct options indexes+1 — Aakash Garg, May 24 '20 at 18:42

score 1 · Accepted Answer · answered May 24 '20 at 18:54

function funcWhichNeedCorrectAnswerIndicesPlusOne(indices) {
 console.log(indices)
}

function getCorrectAnswers(question) {
  funcWhichNeedCorrectAnswerIndicesPlusOne(question.options
     .filter(option => option.correct)
     .map(option => question.options.indexOf(option) + 1)
  )   
}

const question = {
 options: [{
   correct: true
  }, {
    correct: false
  }, {
    correct: true
  }
]}

getCorrectAnswers(question)

score 0 · Answer 2 · answered May 24 '20 at 18:39

0

You can use .filter() instead of .findIndex().

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/filter

answered May 24 '20 at 18:39

AzloD

86
4

score 0 · Answer 3 · answered May 24 '20 at 18:40

0

question.options.filter(item => item.correct).map((item, index) => index+1);

answered May 24 '20 at 18:40

Aakash Garg

10,649
2
7
25

1

Yes I will. Thanks again. – integral100x May 24 '20 at 18:47

score 0 · Answer 4 · answered May 24 '20 at 18:44

0

use the following function, is adapted from this

function getAllIndexes(arr, val) {
    var indexes = [], i;
    for(i = 0; i < arr.length; i++)
        if (arr[i] === val)
            indexes.push(i);
    return indexes;
}

answered May 24 '20 at 18:44

Malintha Ranasinghe

470
3
9

How do I retrieve all indexes that match condition in JavaScript?

4 Answers4