javascript object key key-value creation

How does one create an object based on the precedence of another object's key order?

I have an object like this -

const obj = {
    'veh1': 'Car',
    'veh2': 'Bicycle',
    'veh3': 'Truck',
    'wheels1': '4',
    'wheels2': '2',
    'wheels3': '8'
}

I want an object which have entries mapped like- veh1 to wheels1, veh2 to wheels2, veh3 to wheels3 and so on The resultant object should be like this-

const result = {
    'Car': '4',
    'Bicycle': '2',
    'Truck': '8'
}

I know, we can do it directly like this -

{
   [obj.veh1]: obj.wheels1,
   [obj.veh2]: obj.wheels2,
   [obj.veh3]: obj.wheels3
}

But what will be the better way? The number of entries can be any number 'n'.

How can I attain this through javascript?

Solution

Create entries (key value pairs) from the provided object.
Sort the entries by each of an entry's key.
Finally create a new objects from the upper (or left) as well the lower (or right) half of the before sorted entries.

function localeCompare(a, b) {
  return (a.localeCompare && b.localeCompare
    && a.localeCompare(b))
    || (((a < b) && -1) || ((a > b) && 1) || 0);
}

function compareEntriesByKey(entryA, entryB) {
  return localeCompare(entryA[0], entryB[0]);
}

function createKeyValuePairFromSortedEntryHalfs(obj, $, idx, entries) {
  if (((idx + 1) % 2) === 0) {
 
    const keyIdx = ((idx - 1) / 2);
    const valueIdx = (keyIdx + Math.floor(entries.length / 2));

    const key = entries[keyIdx][1];
    const value = entries[valueIdx][1];

    obj[key] = value;
  }
  return obj;
}


const obj = {
  'wheels3': '8',
  'veh3': 'Truck',
  'wheels1': '4',
  'veh1': 'Car',
  'wheels2': '2',
  'veh2': 'Bicycle',
}
const result = Object
  // (1) create entries (key value pairs) from the provided object.
  .entries(obj)
  // (2) sort the entries by each of an entry's key.
  .sort(compareEntriesByKey)
  // (3) finally create a new objects from the upper (or left) as
  //     well the lower (or right) half of the before sorted entries.
  .reduce(createKeyValuePairFromSortedEntryHalfs, {});

console.log('result :', result);

console.log('obj', obj);
console.log(
  'Object.entries(obj).sort(compareEntriesByKey)',
  Object.entries(obj).sort(compareEntriesByKey)
);

console.log(
  'proof of being a generic approach...', `
  Object.entries({
    'foo-biz': 'biz',
    'x': 111,
    'foo-baz': 'baz',
    'y': 222,
    'foo-bar': 'bar',
    'z': 333,
  }).sort(
    compareEntriesByKey
  ).reduce(
    createKeyValuePairFromSortedEntryHalfs,
    {}
  ) =>`, Object.entries({
    'foo-biz': 'biz',
    'x': 111,
    'foo-baz': 'baz',
    'y': 222,
    'foo-bar': 'bar',
    'z': 333,
  }).sort(
    compareEntriesByKey
  ).reduce(
    createKeyValuePairFromSortedEntryHalfs,
    {}
  )
);

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