Javascript event-driven data object

data.js

var data = {
  _value: undefined,
  _handlers: [],
  set: function(val, cb){
    this._value = val;
    this.attach(cb);
    this._handlers.forEach(function(cb){cb();});
  },
  get: function() {return this._value;},
  attach: function(cb) {
    if (cb && this._handlers.indexOf(cb) === -1) {
      this._handlers.push(cb);
    }
  },
  detach: function(cb) {
    if (cb && this._handlers.indexOf(cb) !== 0) {
      this._handlers.splice(this._handlers.indexOf(cb),1);
    }
  }
};