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what is the best way to convert an object of arrays to an array of objects and vice-versa

{
  category : ['a','b','c'],
  title : ['e','f','g'],
  code : ['z','x','v']
}

To

[
  {
    category : 'a',
    title : 'e',
    code : 'z'
  },
  {
    category : 'b',
    title : 'f',
    code : 'x'
  },
  {
    category : 'c',
    title : 'g',
    code : 'v'
  },
]

what is the best way to convert an object of arrays to an array of objects and vice-versa

{
  category : ['a','b','c'],
  title : ['e','f','g'],
  code : ['z','x','v']
}

To

[
  {
    category : 'a',
    title : 'e',
    code : 'z'
  },
  {
    category : 'b',
    title : 'f',
    code : 'x'
  },
  {
    category : 'c',
    title : 'g',
    code : 'v'
  },
]

• javascript
• arrays
• object
• ecmascript-6

Share Improve this question Follow edited Feb 20, 2017 at 10:51 amir hosein ahmadi asked Feb 20, 2017 at 10:49 amir hosein ahmadiamir hosein ahmadi 26211 silver badge1212 bronze badges 3

• Object.keys() + Array.reduce() – Shilly Commented Feb 20, 2017 at 10:51
• @amir, it is working for you ? – Mihai Alexandru-Ionut Commented Feb 20, 2017 at 11:29
• @amirhoseinahmadi, don't forget to accept an answer in order to help other people. – Mihai Alexandru-Ionut Commented Feb 20, 2017 at 13:38

Add a ment  | 

4 Answers 4

Sorted by: Reset to default 6

You could use two function for generating an array or an object. They works with

• Object.keys for getting all own property names,

• Array#reduce for iterating an array and collecting items for return,

• Array#forEach just fo itarating an array.

function getArray(object) {
    return Object.keys(object).reduce(function (r, k) {
        object[k].forEach(function (a, i) {
            r[i] = r[i] || {};
            r[i][k] = a;
        });
        return r;
    }, []);
}

function getObject(array) {
    return array.reduce(function (r, o, i) {
        Object.keys(o).forEach(function (k) {
            r[k] = r[k] || [];
            r[k][i] = o[k];
        });
        return r;
    }, {});
}

var data = { category: ['a', 'b', 'c'], title: ['e', 'f', 'g'], code: ['z', 'x', 'v'] };

console.log(getArray(data));
console.log(getObject(getArray(data)));

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

You can use map() and forEach()

var obj = {
  category : ['a','b','c'],
  title : ['e','f','g'],
  code : ['z','x','v']
}

var result = Object.keys(obj).map(function(e, i) {
  var o = {}
  Object.keys(obj).forEach((a, j) => o[a] = obj[a][i])
  return o
})

console.log(result)

Here is solution using reduce method and arrow function.

var obj={
  category : ['a','b','c'],
  title : ['e','f','g'],
  code : ['z','x','v']
}
var result=obj[Object.keys(obj)[0]].reduce((a,b,i)=>{
  var newObj={};
  Object.keys(obj).forEach(function(item){
     newObj[item]=obj[item][i];
  });
  return a.concat(newObj);
},[]);
console.log(result);

Not an answer to the original question, but thought I'd share this as I came here looking for a solution to a related problem: I needed the Cartesian product of values of uneven length. What I'm using for that:

/**
 * Get the Cartesian product of a list of array args.
 */
const product = (...args) => args.length === 1
  ? args[0].map(x => [x])
  : args.reduce(
    (a, b) => Array.from(a).flatMap(
        v1 => Array.from(b).map(v2 => [v1, v2].flat())
    )
  );

/**
 * Map[String,Array[Any]] -> Array[Map[String,Any]]
 */
const arrayValuesToObjectArray = (obj) =>
  product(...Object.values(obj)).map(values => Object.fromEntries(
    Object.keys(obj).map((k, idx) => [k, values[idx]])
  ));


console.log(arrayValuesToObjectArray({
  hello: ["this", "is", "a", "test"]
}));

console.log(arrayValuesToObjectArray({
  one: ["foo"],
  two: ["bar", "baz"],
  three: ["this", "is", "three"],
}));

console.log(arrayValuesToObjectArray({
  one: "foo",
  two: "bar baz",
  three: "this is three",
}));

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