event-intercept

Intercept event data before it reaches the listeners.

var intercept = require('event-intercept')
var foo = new EventEmitter()

// Map all data on 'hello' event to uppercase
intercept(foo, 'hello', (args, done) => {
  done(null, args.map(data => data.toUpperCase()))
})

foo.on('hello', console.log)

foo.emit('hello', 'world', 'foo', 'bar')
// WORLD FOO BAR

Useful for injecting where you want to view/change data before it reaches listeners. Like parsing, logging, debugging, etc.

Installation

$ npm install --save event-intercept

Usage

intercept(emitter, event, handler)

Intercepts an event and it's data. These are executed in the order they are added.

Parameters

• emitter (EventEmitter): The emitter you want to add intercepting on.
• event (String): Name of the event you want to intercept.
• handler (Function): A mapping function with the signature (args, done).

Handler

The handler has the parameters (args, done), and you call done with parameters (end, args). Where end can be true (abort safely) or an Error.

Example

intercept(emitter, 'message', function (args, done) {
  // Reverse
  args = args.map(x => x.split('').reverse().join(''))
  // Callback
  done(null, args)
})

License

MIT © Jamen Marz