1

I have an array of objects that looks like this:

arr = [
  {name: "john", age: 23},
  {name: "mary", age: 40},
  {name: "zack", age: 17}
]

I am trying to convert it into something like this:

{
name: ["john", "mary", "zack"],
age: ['23', 40, 17]
}

i have tried the following

arr.map(item => item.name)
arr.map(item => item.age)
return {names, ages}

and it works fine but this assumes that you already know, beforehand, the keys of the objects you're converting.

I want to be able to load the object keys and corresponding array of values dynamically. Assuming i don't know that the objects in our example array have "name" and "age" as keys.

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6 Answers 6

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2

You could reduce the array and the entries of the object and collect the values in the group of the keys.

const 
    data = [{ name: "john", age: 23 }, { name: "mary", age: 40 }, { name: "zack", age: 17 }],
    result = data.reduce((r, o) => Object.entries(o).reduce((t, [k, v]) => {
        if (!t[k]) t[k] = [];
        t[k].push(v);
        return t;
    }, r), {});

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

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0

You could get the key of the first element and then map through it. With each, get its corresponded values

const arr = [
  { name: "john", age: 23, gender: "male" },
  { name: "mary", age: 40, gender: "female" },
  { name: "zack", age: 17, gender: "male" },
]

const res = Object.keys(arr[0]).reduce((acc, el) => {
  const values = arr.map((item) => item[el])
  return { ...acc, [el]: values }
}, {})

console.log(res)

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Just one thing with this approach is like, for some reason if the first object is not having some of the keys(for eg., consider gender is not present in arr[0]), then it might not be present in the output at all.
0

Assuming that each object in your list has the same keys you could get the keys of the first object

const keys = Object.keys(arr[0])

and then map through the keys with your above approach

const returnObj = {}
keys.forEach(key => {
   returnObj[key] = arr.map(item => item[key])
})
return returnObj
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0

You can use Object.entries for the mapping.

var arr = [
  {name: "john", age: 23},
  {name: "mary", age: 40},
  {name: "zack", age: 17}
];

var entries = arr.map((item) => Object.entries(item));

var result = {};
entries.forEach(entry => {
  entry.forEach(item => {
    if (result[item[0]] && result[item[0]].length > 0) {
      result[item[0]].push(item[1]);
    } else {
        result[item[0]] = [item[1]];
    }
  });
});
console.log(result);

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0

You can make use of Array.reduce and Object.keys.

let arr = [
  {name: "john", age: 23},
  {name: "mary", age: 40},
  {name: "zack", age: 17}
]

const formatData = (data) => {
  return data.reduce((res, obj) => {
    Object.keys(obj).map(d => {
      res[d] = [...(res[d] ||[]), obj[d]]
    })
    return res;
  }, {})
}

console.log(formatData(arr))

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Comments

0

You can do this with Ramda

import { mergeWith, concat } from “Ramda”

const mergeConcat = mergeWith(concat)

mergeConcat(arr)
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