generator-collector

♻️ Lazily collect and query generators in JS

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⚠️ This project is experimental and should not be considered stable for production use.

Features

• Collect and query generator results using coroutines
• Iterate only to the values you need, only when you need them
• Seamless integration with promises and async functions

Resources

• 📖 Documentation
• ⚓ Install
• 🔧 API
• 💡 Usage and Examples

Example

The following node example uses generator-collector and js-coroutines to query for the 5 best red wines in France.

import { collector, promiser, each } from 'generator-collector'
import { map, sort } from 'js-coroutines' // optional, but plays nice with other coroutine libraries

async function wine () {
  const categories = ['reds', 'whites', 'sparkling', 'rose', 'dessert', 'port']

  // Create a generator-based "promiser" (coroutine) that loads and sorts a list of wines within a category
  const api = promiser(function* (category = 'reds') {
    const response = yield fetch(`https://api.sampleapis.com/wines/${category}`)
    const data = yield response.json()

    const rated = yield* sort(data, function* (a, b) {
      return yield b.rating.average - a.rating.average
    })

    const items = yield* map(rated, function* (item) {
      return yield { ...item, category }
    })

    return items
  })

  // Create a collector that reduces each result from the queried API responses into a single collection
  const load = collector(function* (query = null) {
    yield* each(query ?? categories, api)
  }, {
    // Override default insert behavior of `push.call` (now `push.apply`).
    // Enables flat reduction of each item in the API responses ([a, b, c] vs. [[a], [b], [c]]).
    insert: (store, value) => Array.prototype.push.apply(store, value)
  })

  // Invoke our data fetching collector for red wines (call `load()` instead for all wine categories)
  const query = load(['reds'])

  // Load all the red wines from the API (since we need the full list to know the "best")
  const all = await query.all()

  // Scan results for the top 5 best red wines from France
  const best = await query.take(5, (item) => item.location.startsWith('France'), true)

  return { all, best }
}

wine().then(result => {
  console.log('Loaded best red wines in France', result.best, result.all.length)

  process.exit(0)
})

Contact & Support

• Create a GitHub issue for bug reports, feature requests, or questions
• Add a ⭐️ star on GitHub or ❤️ tweet to support the project!

License

Copyright © Erik Vavro. All rights reserved.

Licensed under the MIT License.