Convert object to array, insert value between array indexes

Question

I have one question I send form from client to server and get object which checkbox is true and here is problem. e.g. '0': true, '3':true and I would like that my array looks [true,false,false,true], but now I get array like this [true, true] I use map. So in short between object true i would insert false. Please look on my code:

var correctAns = [];
var quizCorrectAnswer = 
    { '0': { '0': true },
      '1': { '0': true, '3': true },
      '2': { '2': true } 
     }
for(correct in quizCorrectAnswer){
  correctAns.push(Object.keys(quizCorrectAnswer[correct]).map((k) => 
  quizCorrectAnswer[correct][k]))
}

I would like receive following arrays: 0: [true], 1: [true, false, false, true], 2: [false, false, true] but now I get 0: [true], 1: [true, true], 2: [true]

@NinaScholz The last is [false, false, true] in his question. — Blue
– Blue, Commented Jan 12, 2018 at 19:33

Blue · Accepted Answer · 2018-01-15 15:37:31Z

1

This should be what you're looking for:

var correctAns = {};
var quizCorrectAnswer = 
    { '0': { '0': true },
      '1': { '0': true, '3': true },
      '2': { '2': true } 
     }
     
Object.keys(quizCorrectAnswer).forEach((question) => {
  correctAns[question] = Object.keys(quizCorrectAnswer[question]).reduce((prev, key) => {
    while (prev.length < key) {
      prev.push(false);
    }
    prev.push(true);
    return prev;
  }, []);
});

console.log(correctAns);

If you want correctAns to simply be an array, use this instead:

var quizCorrectAnswer = 
    { '0': { '0': true },
      '1': { '0': true, '3': true },
      '2': { '2': true } 
     }
     
var correctAns = Object.keys(quizCorrectAnswer).map((question) => {
  return Object.keys(quizCorrectAnswer[question]).reduce((prev, key) => {
    while (prev.length < key) {
      prev.push(false);
    }
    prev.push(true);
    return prev;
  }, []);
});

console.log(correctAns);

edited Jan 15, 2018 at 15:37

answered Jan 12, 2018 at 19:29

Blue

23k7 gold badges69 silver badges102 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

sidhuko Over a year ago

You could replace forEach with map to tidy this up :)

sidhuko Over a year ago

const myO = {a:1,b:2}; const myA = Object.keys(myO).map((i) => myO[i]). Then myA will be an array. It's FRP so you can maintain a 'pure function'

Blue Over a year ago

@sidhuko Took your suggestion for the second code snippet. Don't think it's possible in the second one (easily, without crazy es6 modifiers, or something like underscore.js) to keep the keys as is with mapping.

Nina Scholz · Accepted Answer · 2018-01-12 19:31:31Z

The problem is, you map the keys which return an array with only the given answers. But you need an array with the holes and their false values.

To iterate a sparse array with an array method, you need to convert it into an array without sparse elements and then map a boolean value.

var quizCorrectAnswer = { 0: { 0: true }, 1: { 0: true, 3: true }, 2: { 2: true } },
    correctAns = [],
    correct,
    temp;
    
for (correct in quizCorrectAnswer) {
    temp = [];

    Object
        .keys(quizCorrectAnswer[correct])
        .forEach(k => temp[k] = quizCorrectAnswer[correct][k])

    correctAns.push(Array.apply(null, temp).map(Boolean));
}

console.log(correctAns);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Jonas Wilms · Accepted Answer · 2018-01-12 19:38:13Z

0

  const result = {};
  for(const [key, obj] of Object.entries(quizCorrectAnswer))
     result[key] = Array.from({...obj, length:5}, el => !!el);

You could use Array.from to convert the object into an array. Instead of the static length of 5, you could also take Object.keys(obj).length

answered Jan 12, 2018 at 19:38

Jonas Wilms

139k20 gold badges164 silver badges164 bronze badges

Comments

Mikhail Zharnikov · Accepted Answer · 2018-01-12 19:34:56Z

-1

That's the problem of non-appeared keys and values. Here in quizCorrectAnswer variable value about key '1', there are only '0' and '3' keys. No '1' or '2' key and value is defined in that value. And Javascript map function matches the existing keys to values and so you can get only [true, true] about '1' key (because there are only 2 keys in that value). So to get the result you want, you have to change the quizCorrectAnswer value as follows.

var quizCorrectAnswer = 
    { '0': { '0': true },
      '1': { '0': true, '1': false, '2': false, '3': true },
      '2': { '0': false, '1': false, '2': true}
    };

answered Jan 12, 2018 at 19:34

Mikhail Zharnikov

1781 silver badge13 bronze badges

1 Comment

Blue Over a year ago

Changing input = not a solution.

Collectives™ on Stack Overflow

Convert object to array, insert value between array indexes

4 Answers 4

3 Comments

Comments

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

3 Comments

Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related