How to transform object into sorted array by Lodash

Question

How to transform {2:'b',3:'c',1:'a'} into [{1:'a'},{2:'b'},{3:'c'}] by lodash?

Answer 1

It's fairly trivial using Object.keys + Array.map, you really don't need lodash:

const obj = {2:'b',3:'c',1:'a'};
const arr = Object.keys(obj).map(key => ({ [key]: obj[key] }))

console.log(arr)

Regarding the lack of a sort function, the above code is exploiting the fact that numerically indexed Object keys are (per the spec) stored sequentially. Check the order for yourself:

console.log({2:'b',3:'c',1:'a'})

Here is the relevant portion of the spec

9.1.12 [[OwnPropertyKeys]] ( )

When the [[OwnPropertyKeys]] internal method of O is called the following steps are taken:

1. Let keys be a new empty List.

2. For each own property key P of O that is an integer index, in ascending numeric index order

   2a. Add P as the last element of keys.

Answer 2

With upcoming Javascript with Object.entries, you could map a new array with single objects.

var data = {2:'b',3:'c',1:'a'},
    result = Object
        .entries(data)
        .sort((a, b) => a[0] - b[0])
        .map(([k, v]) => ({ [k]: v }));

console.log(result);

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With lodash, you could use

• _.chain,
• _.toPairs,
• _.sortBy,
• _.map and
• _.fromPairs

var data = {2:'b',3:'c',1:'a'},
    result = _
        .chain(data)
        .toPairs(data)
        .sortBy([0])
        .map(o => _.fromPairs([o]));

console.log(result);

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<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.15.0/lodash.min.js"></script>

Answer 3

Lodash is not really necessary to accomplish what you want, but I'm still adding it anyway and add a sorted function. I've also included the native JavaScript way.

const obj = {b: 3, c: 2, a: 1};


const sortByKeys = object => {
  const keys = Object.keys(object)
  const sortedKeys = _.sortBy(keys)

  return _.map(sortedKeys, key => ({ [key]: object[key]}))
}

// the lodash way, and sorted
console.log(sortByKeys(obj))

// simpler way
const result = Object.keys(obj)
  .map(key => ({ [key]: obj[key] }))
  
 console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.js"></script>

Answer 4

Why use lodash? Just use regular Javascript. Solution can be cleaned up a bit but the idea is to loop through your object and push your desired format into a new array. I also throw the sorting in there for convenience, but feel free to re-factor to your liking.

const obj = {2:'b',3:'c',1:'a'}

let newArr = [];
for (var key in obj) {
  newArr.push({[key]: obj[key]})
  newArr.sort((a, b) => a[key] > b[key])
}
console.log(newArr)