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1.0.2 • Public • Published

After Event Emitter

npm install after-events

Publisher/Subscriber Pattern implementation.

Differences from Node's EventEmitter

  • .after(cb) method (see below)
  • Listeners that throw errors are caught and logged to console.
  • Listeners happen during their own turn.
  • Listener can only listen a maximum of one time with .on()
  • "removeListener" is called "off"
  • No way to see if the listener is listening. (unused)
  • No "addListener" alias
  • No domains (unused)
  • No erroring on unhandled error event. (unused)
  • No maximum listener count. (unused)
  • No prototype/No new needed to create.

If you need one of the features this lacks that is marked unused, feel free to send a pull request/file an issue.

after(callback: function (err: Error U undefined, res: Any U undefined, type: String, ...args: Any)): undefined

  • callback is ran after every listener returns.
  • First parameter to the callback is the error/rejected value of the listener, if there is one.
  • Second parameter to the callback is the return value of the listener, if there is one.
  • The rest of the parameters are the parameters sent to the .emit() that triggered the listener.
  • Calling it multiple times adds more callbacks to be called in order of addition.


// This is really contrived!

var eventEmitter = require('after-events');
var format = require('util').format;

eventEmitter.after(function (err, ret, eventname, eventarg) {
    console.log(format('%s + 1 = %s', eventarg, ret));

eventEmitter.on('number', function (number) {
    return number + 1;

eventEmitter.emit('number', 2);
// Console logs '2 + 1 = 3'

eventEmitter.emit('number', 5);
// Console.logs '5 + 1 = 6'

For a realistic example, see https://github.com/Tennu/tennu/blob/master/lib/command-handler.js.

Tests and Building

To build the test file, use ./fez.js.

To run the test file, use mocha test.js.


npm i after-events

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