In many websites, there are static portions of the page such as the navigation or header that rarely change. If we could deliver the markup for navigation, the experience would feel a bit snappier while the rest of the page is generated.
Try running this snippet in node and visit localhost:3000/incremental and localhost:3000/blocking.
These are pretty trivial examples but we could cache and immediately send the nagivation bar and <head> elements for every request.
| var http = require('http'); | |
| var port = process.env.port || 3000; | |
| var server = http.createServer(); | |
| var log = function(req) { | |
| console.log(req.method + ' ' + req.url); | |
| }; | |
| var router = { | |
| '/progressive': function(req, res) { | |
| res.statusCode = 200; | |
| res.setHeader("Content-Type", "text/html"); | |
| res.write([ | |
| '<html>' | |
| , ' <head>' | |
| , ' <script src="//code.jquery.com/jquery-1.11.2.min.js"></script>' | |
| , ' <style type="text/css">' | |
| , ' html, body {' | |
| , ' background: red;' | |
| , ' font-family: sans-serif;' | |
| , ' }' | |
| , ' </style>' | |
| , ' </head>' | |
| , ' <body>' | |
| , ' <h1>Hello world</h1>' | |
| ].join('\n')); | |
| setTimeout(res.write.bind(res, '<h1>blah</h1>'), 5000); | |
| setTimeout(res.write.bind(res, [ | |
| '<style type="text/css">' | |
| , ' html, body {' | |
| , ' background: blue;' | |
| , ' }' | |
| , '</style>' | |
| ].join('\n')), 8000); | |
| setTimeout(res.write.bind(res, '<h1>blah</h2>'), 10000); | |
| setTimeout(res.write.bind(res, '</body></html>'), 15000); | |
| setTimeout(res.end.bind(res), 20000); | |
| }, | |
| '/blocking': function(req, res) { | |
| res.statusCode = 200; | |
| res.setHeader('Content-Type', 'text/html'); | |
| setTimeout(function() { | |
| res.write('one<br>two<br>three<br>four<br>'); | |
| res.end(); | |
| }, 4000); | |
| } | |
| }; | |
| var route = function(req, res) { | |
| log(req); | |
| if (req.url in router) { | |
| router[req.url].call(router, req, res); | |
| } else { | |
| res.write('Could not find route ' + req.url); | |
| res.statusCode = 404; | |
| res.end(); | |
| } | |
| }; | |
| server.on('request', route); | |
| server.listen(port, function() { | |
| console.log('listening on port', port); | |
| }); |