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A tiny framework for building diff based interactive command line tools.

npm install diffy

Build Status

Basically React, but in the terminal powered by ansi-diff and neat-input.


var diffy = require('diffy')()
var trim = require('diffy/trim')
diffy.render(function () {
  return trim(`
    Hello user. The time is:
      ${new Date()}
    That is all for now
// re-render every 1s
setInterval(() => diffy.render(), 1000)

You can also use diffy to query input from a user

var input = require('diffy/input')({style: style})
var names = []
input.on('update', () => diffy.render())
input.on('enter', (line) => names.push(line))
diffy.render(function () {
  return trim(`
    Enter your name: ${input.line()}
    List of names: ${names.join(' ')}
function style (start, cursor, end) {
  return start + '[' + (cursor || ' ') + ']' + end

See the examples folder for more.


var diffy = require('diffy')([options])

Make a new diffy instance. Writes to stdout.

Options include:

  fullscreen: true // overtake the terminal like vim/less does

Note that if you use fullscreen: true, the terminal will be restored on exit, even if your program crashes.


Trigger a render and/or update the default render function. A render function should simply return a string containing the output you wish to display and then diffy will make sure to only print the diff.


Property containing the width of the terminal.


Property containing the height of the terminal.


Emitted when the terminal is resized. Triggers a render as well.


Emitted just before a render happens.

var input = require('diffy/input')()

Get a neat-input instance. Use this if you want to accept interactive input.

var trim = require('diffy/trim')

Helper function that trims the indentation of a multiline string. Useful if you have a render function that returns an indented string like in the above example.


With diffy, components are just strings you compose together to form your application. A bunch of modules already exists for this pattern, providing useful features.


Thank you to @Fouad for donating the module name.