queue-emitter.js

var Emitter = require('emitter');
var slice = [].slice;

module.exports = QueueEmitter;

function QueueEmitter(){
  if( !(this instanceof QueueEmitter) ){
    return new QueueEmitter();
  }
  this.queued = {};
}

Emitter(QueueEmitter.prototype);

var emit = QueueEmitter.prototype.emit;
QueueEmitter.prototype.emit = function(event){
  var q = this.queued[event] = (this.queued[event] || []);
  q.push(slice.call(arguments));
}

QueueEmitter.prototype.flush = function(event){
  if( this.queued[event] ){
    var q = this.queued[event];
    for(var i=0; i<q.length; i++){
      emit.apply(this, [event].concat(q[i]));
    }
  }
}

QueueEmitter.prototype.reset = function(event){
  if( event ){
    this.queued[event] = [];
  } else {
    this.queued = {};
  }
}


var a = QueueEmitter();
a.on('hi', console.log.bind(console, 'hi'));
a.on('no', console.log.bind(console, 'no'));
a.on('oh', console.log.bind(console, 'oh'));

// nothing happens (queued)
a.emit('hi', 1);
a.emit('hi', 2);
a.emit('hi', 3);
a.emit('hi', 4);
a.emit('no', 1);
a.emit('no', 2);
a.emit('ok', 1);

a.flush('hi'); // 4 emits happens
a.flush('hi'); // 4 emits happen again (in case needed in multiple systems)
a.flush('no'); // 2 emits happens
a.flush('oh'); // 0 emits happens
a.flush('ok'); // 1 emits happens, no listeners though...

a.reset('no'); // part of queue is cleared

a.flush('hi'); // 4 emits still happens
a.flush('no'); // 0 emits happens. cleared.

a.reset(); // entire queue is cleared

a.flush('hi'); // 0 emits happens
a.flush('no'); // 0 emits happens
a.flush('oh'); // 0 emits happens
a.flush('ok'); // 0 emits happens