Sort array of objects, add sorted index to each object, then return to original sorting

Question

I have an array:

  const array = [
    { name: 'b' },
    { name: 'a' },
    { name: 'c' },
  ]

The goal here is to keep the same array but to add a new property on each object based on its position if the array was sorted:

  const array = [
    { name: 'b', sortIndex: 1 },
    { name: 'a', sortIndex: 0 },
    { name: 'c', sortIndex: 2 },
  ]

I came up with a plan to just sort the array based on the name. Then loop through it and add the index to get this:

 const array = [
   { name: 'a', sortIndex: 0 },
   { name: 'b', sortIndex: 1 },
   { name: 'c', sortIndex: 2 },
 ]

Then I would loop through the original array and do a findIndex against the sorted array to get the index but that seems like terrible code with so many loops and stuff. Any ideas on how to make this better?

export function setSortIndexes(series) {
  const clone = cloneDeep(series);
  const sorted = orderBy(clone, [
    (x) => (x.name ? x.name.toLowerCase() : null),
  ]);

  sorted.forEach((x, i) => {
    x.sortIndex = i;
  });

  series.forEach(x => {
    const index = sorted.findIndex((s) => s.name === x.name);

    if (index !== -1) {
      x.sortIndex = sorted[index].sortIndex;
    }
  });

  return series;
}

codereview.stackexchange.com might be a better place for this question. — Charlie Bamford
– Charlie Bamford, Commented Jun 14, 2021 at 23:13
@ChrisG thats alot better than what i have and it works well. thanks! — cup_of
– cup_of, Commented Jun 14, 2021 at 23:21

Matt · Accepted Answer · 2021-06-15 00:12:50Z

1

Create a temporary array to sort, including the original index.
Sort by the name field
Add index to the original object.

array
  .map((e, i) => ({ name: e.name, originalIndex: i }))
  .sort((a, b) => a.name.localeCompare(b.name))
  .forEach((e, i) => array[e.originalIndex].sortIndex = i)

edited Jun 15, 2021 at 0:12

answered Jun 14, 2021 at 23:25

Matt

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Mister Jojo · Accepted Answer · 2021-06-15 11:59:13Z

1

you can do that:
no need to duplicate objects (or some of its elements) in a new array. an array of pointers to these objects is sufficient

const array = 
  [ { name: 'b'} 
  , { name: 'a'} 
  , { name: 'c'} 
  ] 
array                  // create a new array  
  .map(o=>({o}))      // of pointers ( o ) to refer each array objects
  .sort((a,b)=>a.o.name.localeCompare(b.o.name)) // sort 
  .forEach((_,i,a)=>a[i].o.sortIndex = i )      // add the sortIndex attr 


console.log(array)

edited Jun 15, 2021 at 11:59

answered Jun 14, 2021 at 23:25

Mister Jojo

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