AJAX crawling / JavaScript SEO for MEAN stack web apps

seo-express-filter.js

/*
 * Redirect _escaped_fragment_ requests to SEO server for HTML snapshots
 * 
 * Place in your middleware stack. Watch out for correct placement:
 *   - after any static handler
 *   - before app routes (router)
 * 
 * app.use(require('./seo-express-filter')(app))
 * 
 */

var URL = require('url')
var httpProxy = require('http-proxy')

module.exports = function(app) {

	var conf = app.config.seo
	var seoServerUrl = URL.format({
		protocol: 'http',
		hostname: conf.host || 'localhost',
		port: conf.port || 8888
	})

	var proxy = httpProxy.createProxyServer({
		target: seoServerUrl
	});

	return function(req, res, next) {
		if (!/[&\?]_escaped_fragment_=/.test(req.url) || req.method != 'GET') {
			return next()
		}
		console.log('Proxying request', req.url)
		proxy.web(req, res, function(err) {
			console.error('Unable to proxy request', err)
			// pass through on error - avoid failure on bot request
			next()
		})
	}
}