@baethon/promise-duck

promise-duck

Converts given callback to Thenable object.
Such object is compatible with Promise spec so it can be used as it was a real Promise.

The difference is that computation is deferred until then() method is called or await keyword is used.
It's quite fair to say that in the way how it works such Promise is quite similar to Task

• why?
• installation
• usage
• development

why?

The idea came from little support library which was responsible for building a query (using sort-of fluent API) which was responsible for checking if given value is unique in the database.

I was wondering if object with then() method can be used as a regular Promise. Turned out that its possible.

This little discovery opened me a way to define friendly syntax:

const emailUnique = await isUnique.in('users').where({ email: '[e-mail]' })

The defined object can be stored in a variable and none query will be executed until calling then() or using await keyword.

// define details of query (no query is executed!)
const query = isUnique.in('users').where({ email: '[e-mail]' })

// query the database and return the results
const emailUnique = await query

installation

npm i @baethon/promise-duck

# or with yarn
yarn add @baethon/promise-duck

usage

Package exposes two functions:

• thenable() converts given function to Thenable object.
• bind() converts given function and binds it to the selected object

thenable()

const { thenable } = require('@baethon/promise-duck')

const heavyStuff = Math.random
const p = thenable(heavyStuff)

const result = await p

bind()

const { bind } = require('@baethon/promise-duck')

const heavyStuff = function () {
  return `Hello ${this.name}`
}

const object = { name: 'Jon' }

bind(heavyStuff).to(object)

const result = await object

results cache

By default results generated by given function will be cached.

Both, thenable() and bind() allow to disable cache by passing memoize: false option:

const { thenable } = require('@baethon/promise-duck')

const fn = Math.random
const p = thenable(fn, { memoize: false })

development

If you're planning to contribute to the package please make sure to adhere to following conventions.

tests & linting

• lint your code using standard; run npm run lint to check if there are any linting errors
• make sure to write tests for all the changes/bug fixes

issues & PR

• try to provide regression test when you find a bug
• share some context on what you are trying to do, with enough code to reproduce the issue