a neat cli logger for stateful command line applications
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README.md

neat-log

npm travis standard

A neat logger for command line tools, inspired by Choo! I've heard so much about how awesome front-end javascript has gotten, I wanted to bring some of that magic to command line applications. Used in the Dat command line tool.

  • Use easy-to-read strings to create console outputs.
  • Automatically diff template output with existing console (via diffy) (pretty much React for your terminal).
  • Update console output in any order with event based output.
  • Handle command line input via neat-input.
  • Pretty neat!

Example

Each neat logger has two components: a view and functions that modify state and emit events.

var neatLog = require('neat-log')
var output = require('neat-log/output')

var neat = neatLog(view)
neat.use(countTheSeconds)

function view (state) {
  // This gets printed to the console! Wow. So neat.
  return output(`
    Hello World!
    I've been running for ${state.seconds} second${state.seconds === 1 ? '' : 's'}.
  `)
}

function countTheSeconds (state, bus) {
  state.seconds = 0
  setInterval(function () {
    state.seconds++
    bus.emit('render')
  }, 1000)
  bus.emit('render')
}

This example will print to the console:

Hello world!
I've been running for 0 seconds.

And update every second!

More examples:

  • dat - full command line application with multiple views, components, etc.
  • cabal - p2p chat application.
  • count-files - simple example with a single view and use function.
  • basic examples

Components

Neat-log works great with components, just like Choo!

You can use string-based components too! Check out diff components for more.

Install

npm install neat-log

API

Heavily inspired by Choo! If you get confused here, check docs there because they are much nicer =).

var neat = neatLog(view(state), [opts])

  • views is a single function or array of functions that return string(s) to output to the console. views are passed the state as the first argument.
  • opts.logspeed (default 250ms) - throttles how often output is rendered.
  • opts.quiet - shhhh.... do not print anything
  • opts.state - pass in initial state

neat.use(callback(state, bus))

Use a function (state, bus) to change state and emit events via the bus. You can call bus.emit() to emit a new event and bus.on() to listen. Emitter is an instance of nanobus.

bus also has some special functions/events:

bus.render()

Cause an immediate render (normally it'd be throttled). This is helpful to do before exiting.

bus.on('exit')

Handle exit from process.on('SIGINT'). Useful for rendering exit messages, etc. If no handler is provided, process will exit.

neat.render()

For an immediate render. Helpful outside of a use function.

var output = require('neat-log/output')

Get a function to make your template literals nicer. Removes spaces and stuff™.

Combines well with..

Licensing

This package is free to use for noncommercial purposes and for commercial purposes during a trial period under the terms of the Prosperity Public License.

Licenses for long-term commercial use are available via licensezero.com.

licensezero.com pricing