overshadow-listeners

Add an event listener before existing listeners.

#overshadow-listeners

Add an event listener before existing listeners.

Event listeners always fire in the order they are added, yet sometimes we have no control over this ordering and require certain listeners to definitely run before any others.

var http = require('http')
var Overshadow = require('overshadow-listeners')
 
var server = http.createServer(function(reqres) {
  res.end('ok!')
})
 
Overshadow(server).on('request', function(reqres) {
  // This handler runs before any other request handlers 
  // (including the handler supplied to http.createServer!) 
  if (req.url !== '/') return res.end('no.') // reject any requests other than those for '/' 
})
 
Overshadow(server).once('request', function(reqres) {
  // happens only once, before any other request handlers 
})
 
server.listen(9000)

Alternatively, manually detach and reattach listeners:

var overshadow = Overshadow(server)
overshadow.detach('request')
 
// attach whatever listeners you need 
server.on('request', function(reqres) {
  if (req.url !== '/') return res.end('no.')
})
 
overshadow.reattach('request')
// remember to reattach old listeners 

We've included a simple .then(fn) method you can call to make chainable the process of detaching, doing something then reattaching. .then(fn) does nothing but execute the supplied function

Overshadow(server)
.detach('request')
.then(function() { // '.then' executes supplied fn & returns chain  
  server.once('request', function(reqres) {
    if (req.url !== '/') return res.end('no.')
  })
})
.reattach('request') // remember to reattach old listeners 

Licence

MIT