after-events's Introduction

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.

Example

// 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](Tennu's Command Handler).