@MomsFriendlyDevCo/Express-Events

Improved event emitter for express.

This module adds a simple middleware function which transforms res into an event emitter and provides hookable functionality.

All events are executed via Eventer which means all events are async friendly promisable functions which will be waited for before the emitter continues.

var express = require('express');
var expressEvents = require('@momsfriendlydevco/express-events');

var app = express();

// Add into all requests from root onwards (use a prefix to limit)
app.use(expressEvents());


// Log how all endpoints took to respond
app.use((req, res, next) => {
	var startTime = Date.now();
	res.on('end', ()=> {
		console.log('HIT', req.path, 'took', Date.now() - startTime, 'ms');
	});
});


// Log how big the output of any buffer response was
app.use('/buffers', (req, res, next) => {
	res.on('send', output => {
		if (Buffer.isBuffer(output)) console.log('Buffered output for endpoint', req.path, 'is', buffer.length, 'bytes');
		return output; // Pass output to actual outputter
	});
	next();
});


// Glue `{status: 'goodbye'}` onto the end of all JSON requests
app.use('/api', (req, res, next) => {
	res.on('json', payload => {...payload, status: 'goodbye'});
	next();
});

API

Event: end(...args)

Emitted when res.end() gets called with the original arguments.

Event: json(payload)

Emitted on each call to res.json() with the original object payload. Subsequent functions can mutate the output before outputting.

app.get('/api/test/json', (req, res) => {
	res.on('json', payload => ({...payload, bar: 'Bar!'})) // Glue 'bar' key onto output
	res.send({foo: 'Foo!']) // Eventually outputs {foo: 'Foo!', bar: 'Bar!'}
});

Event: redirect(url)

Emitted on each call to res.redirect() with the original URL payload.

Event: sendFile(stream)

Emitted on each call to res.sendFile() with the read stream.