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add extract #5317

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@damianbeles damianbeles commented Nov 22, 2021 •
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Hello 👋. Hope this PR will help many in their software development process.

What is introduced in this PR?

This PR introduces extract function which helps you extract sublists from a given collection and some predicates.

How is extract used?

Let's say we have this array:

const documents = [
  { pages: 24,  type: 'ebook',   category: 'finance', ... },
  { pages: 240, type: 'book',    category: 'self development', ... },
  { pages: 41,  type: 'ebook',   category: 'finance', ... },
  { pages: 66,  type: 'ebook',   category: 'it', ... },
  { pages: 2,   type: 'article', category: 'it', ... }
]

and we want to extract finance ebooks, self development books and documents from it category.

We can do this with extract function I implemented:

const [financeEbooks, selfDevelopmentBooks, itDocuments] = extract(
  documents,
  doc => doc.type === 'ebook' && doc.category === 'finance',
  doc => doc.type === 'book' && doc.category === 'self development',
  doc => doc.category === 'it'
)

Printing these sublists we obtain:

console.log(financeEbooks)
// [ { pages: 24, type: 'ebook', category: 'finance', ... }, { pages: 41, type: 'ebook', category: 'finance', ... }]

console.log(selfDevelopmentBooks)
//  [{ pages: 240, type: 'book', category: 'self development', ... }]

console.log(itDocuments)
//  [{ pages: 66, type: 'ebook', category: 'it', ... }, { pages: 2, type: 'article', category: 'it', ... }]

How would you do this without extract?

const financeEbooks = documents.filter(doc => doc.type === 'ebook' && doc.category === 'finance');
const selfDevelopmentBooks = documents.filter(doc => doc.type === 'book' && doc.category === 'self development');
const itDocuments = documents.filter(doc => doc.category === 'it');

Why the addition of extract?

You won't parse the documents array three times (or N times generally speaking). You'll only parse it once. Also, you'll declare the sublists in the same place, thus making the code easier to read.

@jdalton jdalton closed this Sep 16, 2023
@jdalton jdalton added the issue bankruptcy Closing the issue/PR to start fresh label Sep 16, 2023
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@damianbeles @jdalton