l

L

Mix Async/Sync code with Promises and Streams in a reusable unified line

You have multiple functions, some of them are async, others are promise-based, and you have some stream transformers, and you want to plug everything together: This module takes an array of functions/streams and gives you a single function, that can be used with callback, or as a promise. It takes care of piping consecutive streams, buffering them before passing them to the next function... etc.

Installation

npm install --save l

Features

• A segment can be sync, async with a callback, can return a promise, or can define a stream
• Consecutive streams are automatically piped, only buffered when next segment is not a stream
• You can return a stream, and it will be automatically buffered/piped

Usage Example

const l = require('l');

var calc = l([
  (val) => val * 5, // sync
  { // Split
    add: (val) => Promise.resolve(val + 2), // promise
    mul: (val, done) => process.nextTick(() => done(null, val * 7)) // async
  },
  (composed) => composed.add + composed.mul // Join
])

calc(1, function (error, answer) { // with a callback
  require('assert').strictEqual(answer, 42)
})

calc(Math.PI).then(result => { // as a promise
  console.log(result) // 127.66370614359172
})

For a more complete example that involves streams, please check examples and tests.

Debugging

To enable debugging:

DEBUG=line node ./examples/npm-module-github-stats.js penguin

>executing on: penguin (5 segments)
   0 <async IncomingMessage {   _readableState: [Object],   readable: true,...
   1 @consuming readable stream...
   1 <sync { _id: 'penguin',   _rev: '151-868f4a334cf6a0bc8ced2f4485e7da78',   name: 'penguin',...
   2 <promise etabits/node-penguin
   3 <async IncomingMessage {   _readableState: [Object],   readable: true,...
   4 @consuming readable stream...
   4 <sync { gh: [Object],   npm: [Object] }...
<finished with { gh: [Object],   npm: [Object] }...

Running tests

npm test

Compatibility

• L is compatible with Node.js v6 LTS, Node.js v7 Current, Node.js v5 and Node.js v4

Next (Roadmap)

• Ability to split and rejoin a stream (parallel execution)
• Return a readable stream when last element is a stream (optional)
• Syntactic sugar, once uses cases are established, so we have a stable API
• Browser use?
• objectMode streams between segments
• create objectMode stream duplex instead of a function wrapper
• ...