I want to move past the hello, world example I posted yesterday and show something just a bit larger, the React tutorial. It’s a pretty simple application demonstrating how to nest multiple components to build a simple Comments section. If you’ve already done the React tutorial, there’s nothing new to see here. Without further ado, let’s set up the basic groundwork then jump into the code.


I’ll use the same directory structure as before, though I’ll be adding a few more files.

mkdir -p {build,src/{coffee,stylesheets},www}
touch src/coffee/Comment{,Box,Form,List}.coffee
touch src/coffee/app.coffee
touch www/index.html
touch comments.json
touch server.coffee

I’ll use the same SASS build, and I’ll need to download a couple extra JavaScript files, jQuery and Marked.

(cd src/stylesheets/ ; bourbon install ; neat install ; bitters install)
(cd www; wget http://necolas.github.io/normalize.css/latest/normalize.css)
(cd www; wget https://cdnjs.cloudflare.com/ajax/libs/marked/0.3.2/marked.min.js)
(cd www; wget https://cdnjs.cloudflare.com/ajax/libs/jquery/2.1.1/jquery.min.js)

I’ll start the same build pipeline, except I won’t need the static HTTP server from before: the React tutorial uses a small dynamic server for posting new comments, which I’ll get to below.

sass --watch src/stylesheets/style.sass:www/style.css &
coffee -o build/ -w -c src/coffee/* &
watchify -v -o www/bundle.js build/app.js &

The code

Let’s start with the HTML. Not much has changed since hello, world; just add <script> includes for the jQuery and Marked files we downloaded earlier.


<!DOCTYPE html>
<meta charset="utf-8">
    <link rel="stylesheet" type="text/css" href="normalize.css">
    <link rel="stylesheet" type="text/css" href="style.css">
    <script src="marked.min.js"></script>
    <script src="jquery.min.js"></script>
    <script src="bundle.js"></script>

I’ll reuse the same stub SASS file; you should be able to style this fairly easily given the class names we set up on the components later.


@import 'bourbon/bourbon'
@import 'neat/neat'
@import 'base/base'

Next let’s drop the example comments into a file comments.json at the top level of the project. This won’t be in www/.


        "author": "Pete Hunt",
        "text": "This is one comment"
        "author": "Jordan Walke",
        "text": "This is *another* comment"

The server is a pretty simple Express server. We statically serve everything in www/, provide a GET /comments.json route to retrieve the list of comments, and provide a POST /comments.json route to accept individual comments and return the new list of comments. This file sits next to comments.json in the top-level.


fs = require 'fs'
path = require 'path'
express = require 'express'
bodyParser = require 'body-parser'

app = express()
app.use bodyParser.json()
app.use bodyParser.urlencoded extended: true

app.use '/', express.static path.join __dirname, 'www'

app.get '/comments.json', (req, res) ->
  fs.readFile 'comments.json', (err, data) ->
    res.setHeader 'Content-Type', 'application/json'
    res.send data

app.post '/comments.json', (req, res) ->
  fs.readFile 'comments.json', (err, data) ->
    comments = JSON.parse data
    comments.push req.body
    fs.writeFile 'comments.json', JSON.stringify(comments, null, 4), (err) ->
      res.setHeader 'Content-Type', 'application/json'
      res.setHeader 'Cache-Control', 'no-cache'
      res.send JSON.stringify comments

app.set 'port', process.env.PORT || 3000
app.listen app.get('port'), () ->
  console.log "Listening on :#{app.get 'port'}"

The React code

Finally, we can talk about the React code! There are 4 components and 1 top-level application file.

  1. Comment, which renders an individual comment
  2. CommentList, which renders a list of Comments from JSON
  3. CommentForm, an input form for posting new comments
  4. CommentBox, the outermost component holding a CommentList and the CommentForm


A Comment takes its author and its text content as properties and renders a small div. It uses the marked(..) function from the Marked library included from the HTML.

React = require 'react'
{div, h2, span} = React.DOM

module.exports = React.createFactory React.createClass
  displayName: 'Comment'
  render: ->
    rawComment = marked @props.children.toString(),
      sanitize: true
    div {className: 'comment'},
      h2({className: 'commentAuthor'}, @props.author)
      span(dangerouslySetInnerHTML: {__html: rawComment})


CommentList is even simpler: it takes a JSON array as a property and renders a Comment for each element/comment in the array.

React = require 'react'
{div} = React.DOM

Comment = require './Comment'

module.exports = React.createFactory React.createClass
  displayName: 'CommentList'
  render: ->
    div {className: 'commentList'},
      @props.data.map((comment) ->
        Comment({author: comment.author}, comment.text))


CommentForm takes a property that is a function, onCommentSubmit. This function is provided by the CommentBox component and should handle updating the application state with the new comment; all CommentForm has to do is provide it with a single JSON comment. After calling the handler, it clears out its input fields.

React = require 'react'
{form, input} = React.DOM

module.exports = React.createFactory React.createClass
  displayName: 'CommentForm'
  handleSubmit: (e) ->
    author = React.findDOMNode(@refs.author).value.trim()
    text = React.findDOMNode(@refs.text).value.trim()
    if author and text
      @props.onCommentSubmit author: author, text: text
      React.findDOMNode(@refs.author).value = ''
      React.findDOMNode(@refs.text).value = ''
  render: ->
    form {className: 'commentForm', onSubmit: @handleSubmit},
      input({type: 'text', ref: 'author', placeholder: 'Your name'})
      input({type: 'text', ref: 'text', placeholder: 'Say something...'})
      input({type: 'submit', value: 'POST'})


This is the largest component by far. It, too, takes some properties: the URL endpoint that points to the comments JSON and a polling interval for fetching new comments. Polling isn’t an ideal solution, but it’s adequate for something this small; we’d need a more complicated server.coffee to push new comments out to clients, and it’s mostly orthogonal to the concept of the application.

There are just 2 helper functions: loadCommentsFromServer is called internally to fetch new comments periodically, while handleCommentSubmit is passed down to a child component as a click/submit handler. This is a pretty common pattern, keeping the state & the handler in the parent component, with the child component accessing the handler as a property.

React = require 'react'
{div, h1} = React.DOM

CommentList = require './CommentList'
CommentForm = require './CommentForm'

module.exports = React.createFactory React.createClass
  displayName: 'CommentBox'
  loadCommentsFromServer: ->
      url: @props.url
      dataType: 'json'
      cache: false
      success: (data) =>
        @setState data: data
      error: (xhr, status, err) =>
        console.error @props.url, status, err.toString()
  handleCommentSubmit: (comment) ->
    newComments = @state.data.concat [comment]
    @setState data: newComments
      type: 'POST'
      data: comment
      url: @props.url
      dataType: 'json'
      success: (data) =>
        @setState data: data
      error: (xhr, status, err) =>
        console.error @props.url, status, err.toString()
  getInitialState: ->
    data: []
  componentDidMount: ->
    setInterval @loadCommentsFromServer, @props.pollInterval
  render: ->
    div {className: 'commentBox'},
      h1({}, 'Comments')
      CommentList({data: @state.data})
      CommentForm({onCommentSubmit: @handleCommentSubmit})

The top-level application file renders a CommentBox to document.body and passes the 2 properties, the URL for GET/POSTing the comments JSON, and the poll interval (in milliseconds).


React = require 'react'
CommentBox = require './CommentBox'

React.render CommentBox(url: 'comments.json', pollInterval: 2000),


That’s it! At this point, you should be able to run the server and see a working comment box. If you’ve already done the React tutorial, there’s nothing new here except for the CoffeeScript. Hopefully you see CoffeeScript is roughly as syntax-sugary as JSX, though there are obviously ups and downs to using either one. Happy hacking.

coffee server.coffee 
Listening on :3000