{"rowid": 49, "title": "Universal React", "contents": "One of the libraries to receive a huge amount of focus in 2015 has been ReactJS, a library created by Facebook for building user interfaces and web applications.\nMore generally we\u2019ve seen an even greater rise in the number of applications built primarily on the client side with most of the logic implemented in JavaScript. One of the main issues with building an app in this way is that you immediately forgo any customers who might browse with JavaScript turned off, and you can also miss out on any robots that might visit your site to crawl it (such as Google\u2019s search bots). Additionally, we gain a performance improvement by being able to render from the server rather than having to wait for all the JavaScript to be loaded and executed.\nThe good news is that this problem has been recognised and it is possible to build a fully featured client-side application that can be rendered on the server. The way in which these apps work is as follows:\n\nThe user visits www.yoursite.com and the server executes your JavaScript to generate the HTML it needs to render the page.\nIn the background, the client-side JavaScript is executed and takes over the duty of rendering the page.\nThe next time a user clicks, rather than being sent to the server, the client-side app is in control.\nIf the user doesn\u2019t have JavaScript enabled, each click on a link goes to the server and they get the server-rendered content again.\n\nThis means you can still provide a very quick and snappy experience for JavaScript users without having to abandon your non-JS users. We achieve this by writing JavaScript that can be executed on the server or on the client (you might have heard this referred to as isomorphic) and using a JavaScript framework that\u2019s clever enough handle server- or client-side execution. Currently, ReactJS is leading the way here, although Ember and Angular are both working on solutions to this problem.\nIt\u2019s worth noting that this tutorial assumes some familiarity with React in general, its syntax and concepts. If you\u2019d like a refresher, the ReactJS docs are a good place to start.\n\u00a0Getting started\nWe\u2019re going to create a tiny ReactJS application that will work on the server and the client. First we\u2019ll need to create a new project and install some dependencies. In a new, blank directory, run:\nnpm init -y\nnpm install --save ejs express react react-router react-dom\nThat will create a new project and install our dependencies:\n\nejs is a templating engine that we\u2019ll use to render our HTML on the server.\nexpress is a small web framework we\u2019ll run our server on.\nreact-router is a popular routing solution for React so our app can fully support and respect URLs.\nreact-dom is a small React library used for rendering React components.\n\nWe\u2019re also going to write all our code in ECMAScript 6, and therefore need to install BabelJS and configure that too.\nnpm install --save-dev babel-cli babel-preset-es2015 babel-preset-react\nThen, create a .babelrc file that contains the following:\n{\n \"presets\": [\"es2015\", \"react\"]\n}\nWhat we\u2019ve done here is install Babel\u2019s command line interface (CLI) tool and configured it to transform our code from ECMAScript 6 (or ES2015) to ECMAScript 5, which is more widely supported. We\u2019ll need the React transforms when we start writing JSX when working with React.\nCreating a server\nFor now, our ExpressJS server is pretty straightforward. All we\u2019ll do is render a view that says \u2018Hello World\u2019. Here\u2019s our server code:\nimport express from 'express';\nimport http from 'http';\n\nconst app = express();\n\napp.use(express.static('public'));\n\napp.set('view engine', 'ejs');\n\napp.get('*', (req, res) => {\n res.render('index');\n});\n\nconst server = http.createServer(app);\n\nserver.listen(3003);\nserver.on('listening', () => {\n console.log('Listening on 3003');\n});\nHere we\u2019re using ES6 modules, which I wrote about on 24 ways last year, if you\u2019d like a reminder. We tell the app to render the index view on any GET request (that\u2019s what app.get('*') means, the wildcard matches any route).\nWe now need to create the index view file, which Express expects to be defined in views/index.ejs:\n\n\n
\nThis is the index page
\nA little bit about me.
\n