Restructure objects array

Question

I have an objects array:

[{description: a, category: a},{description: b, category: b},{description: c, category: c}...]

I need to restructure it to this format:

[{category: a, items: [a, b, c, d], priority: 1},{category: b, items: [a, b, c, d], priority: 2},{category: c, items: [a, b, c, d], priority: 10}]

What I did below works and returns the desired result, I'm just wondering if there is a way to shorten it.

const getNewList = items => {
// Filter items to get all categories and set their priority
  let categories: any = [
    ...new Set(
      items.map(item => {
        switch (item.category.toLowerCase()) {
          case 'a':
            return {category: item.category, priority: 1}
          case 'b':
            return {category: item.category, priority: 2}
          case 'c':
            return {category: item.category, priority: 10}
        }
      })
    )
  ]

// Remove duplicate entries
  categories = [
    ...new Map(categories.map(item => [item.category, item])).values()
  ]

// Restructure object - get all items and the priority grouped by category
  const newList = []
  for (var i = 0; i < categories.length; i++) {
    newList.push({
      category: categories[i],
      items: items
        .filter(item=> item.category === categories[i].category)
        .map(item=> {
          return item.description
        }),
      priority: categories[i].priority
    })
  }
  return newList
}

Whenever you find yourself creating a new array and pushing items to it, you probably can just use map to create the new array. — Heretic Monkey
– Heretic Monkey, Commented Sep 13, 2020 at 21:57
Is it true that you know the category to priority mapping before you run through this? that is.. it's always { a: 1, b:2, c:10, d: 100 } ( or whatever )? — mr rogers
– mr rogers, Commented Sep 13, 2020 at 21:58
@mrrogers, yes, I know the priority for each category before I run through it — user3378165
– user3378165, Commented Sep 13, 2020 at 21:59
So each entry in the result is basically a list of descriptions that match the category? in your example, i think i'm confused because it seems like the use of a,b,c,d might be a bit overloaded. — mr rogers
– mr rogers, Commented Sep 13, 2020 at 22:09
Uncaught SyntaxError: unexpected token: ':' on let categories: any = [ — Mister Jojo
– Mister Jojo, Commented Sep 13, 2020 at 22:10

Bergi · Accepted Answer · 2020-09-13 22:08:04Z

2

You might be looking for

function getNewList(items) {
  const categories = new Map([
    ['a', {category: 'a', items: [], priority: 1}],
    ['b', {category: 'b', items: [], priority: 2}],
    ['c', {category: 'c', items: [], priority: 10}],
  ]);
  for (const item of items) {
    categories.get(item.category.toLowerCase()).items.push(item.description);
  }
  return Array.from(categories.values());
}

If you don't want to have empty categories, you can .filter(c => c.items.length) them out.

answered Sep 13, 2020 at 22:08

Bergi

671k162 gold badges1k silver badges1.5k bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Restructure objects array

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related