drupe

Tiny helper that lets you run Mango selectors anywhere you need a JavaScript predicate.

drupe is inspired by the ergonomics of sift but speaks Mango—the JSON-based query language used by CouchDB and PouchDB. Pass a Mango selector in and get back a function that tests plain JavaScript objects, arrays, or any iterable source.

Why drupe?

• Reuse the same Mango selectors you ship to CouchDB/PouchDB on the client or in tests.
• Drop into Array.prototype.filter, find, or any higher-order utility—no extra plumbing required.
• Ships as a single function that delegates to PouchDB’s battle-tested matchesSelector implementation.
• Zero configuration, fully typed, and framework/runtime agnostic.

Installation

Install from JSR:

# npm, bun, and older versions of yarn or pnpm
npx jsr add @holmes/drupe

Quick start

import { drupe } from 'drupe'

const isPublishedTechArticle = drupe({
  type: 'article',
  publishedAt: { $exists: true },
  tags: { $in: ['databases', 'javascript'] }
})

const articles = [
  { type: 'article', slug: 'mango-101', tags: ['databases'], publishedAt: '2024-05-02' },
  { type: 'article', slug: 'draft-post', tags: ['javascript'] },
  { type: 'note', slug: 'retro' }
]

const published = articles.filter(isPublishedTechArticle)
// -> [{ type: 'article', slug: 'mango-101', tags: ['databases'], publishedAt: '2024-05-02' }]

The same selector you use in a db.find() call now works as an in-memory predicate.

More examples

All Mango selector operators are supported because drupe simply forwards to PouchDB’s selector engine. For a full reference, see the PouchDB guide on Mango queries and the CouchDB documentation linked above.

import { drupe } from 'drupe'

const isHighValueCustomer = drupe({
  $and: [
    { spend: { $gte: 1000 } },
    { status: { $in: ['gold', 'platinum'] } }
  ]
})

const customers = [
  { name: 'Ada', spend: 3200, status: 'platinum' },
  { name: 'Lin', spend: 840, status: 'gold' },
  { name: 'Edsger', spend: 1500, status: 'silver' }
]

customers.filter(isHighValueCustomer)
// -> [{ name: 'Ada', spend: 3200, status: 'platinum' }]

You can also use $not, $regex, $size, $elemMatch, and any other Mango operator:

const containsLargeAttachment = drupe({
  attachments: {
    $elemMatch: {
      content_type: { $regex: '^image/' },
      length: { $gt: 1_000_000 }
    }
  }
})

docs.filter(containsLargeAttachment)

API

const predicate = drupe(selector)
predicate(document) // -> boolean

• selector – Any valid Mango selector object.
• Returns a predicate function that can be reused across collections, iterables, or bespoke logic.

TypeScript: The exported signature is intentionally loose—(selector: any) => (subject: unknown) => boolean—so you can refine the shape that makes sense for your app.

How it works

drupe is intentionally tiny:

import { matchesSelector } from 'pouchdb-selector-core'

export const drupe = (selector: any) => (subject: unknown) => {
  return matchesSelector(subject, selector)
}

When you call drupe(selector), it defers entirely to matchesSelector, the same function PouchDB uses internally to evaluate Mango selectors. That means:

• Behaviour matches CouchDB/PouchDB exactly (including quirks and edge cases).
• New Mango features arrive as soon as they land in pouchdb-selector-core.
• There is no custom query engine to maintain.

Related resources

• CouchDB Mango selector reference: https://docs.couchdb.org/en/stable/api/database/find.html
• PouchDB Mango query guide: https://pouchdb.com/guides/mango-queries.html
• Inspiration: sift lets you filter arrays with MongoDB selectors—check it out at https://github.com/crcn/sift.js

License

MIT © Sam Holmes