db.js

function Database(file) {
  this._file = file;
  this._isDirty = false;
  this._isLocked = false;
  this._data = {};
  this._saveDelay = 60 * 1000;
}

Database.prototype = Object.create(EventEmitter.prototype);

Database.prototype._store = function() {
  if (this._isDirty) {
    this._lock();
    fs.writeFile(this._file, JSON.stringify(this._data), function(err) {
      if (err == null) {
        this._isDirty = false;
      } 
      this._unlock();
    }.bind(this))
  }
}

Database.prototype._lock = function() {
  this._isLocked = true;
}

Database.prototype._unlock = function() {
  if (this._isLocked) {
    this._isLocked = false;
    this.emit('unlock');
  }
}

Database.prototype.load = function(cb) {
  this._lock();
  fs.readFile(this._file, function(err, data) {
    if (err) cb(err);
    else {
      this._data = data;
      this._unlock();
      cb()
    }
  }.bind(this))
}

Database.prototype._attempt = function(f) {
  if (this._isLocked) {
    this.on('unlock', f.bind(this))
  } else {
    f.call(this)
  }
}

Database.prototype.set = function(key, value, cb) {
  this._attempt(function() {
    this._data[key] = value;
    this._isDirty = true;
    setTimeout(this._store.bind(this), this._saveDelay);
    cb();
  })
}

Database.prototype.get = function(key, cb) {
  cb(this._data[key]);
}

Can you show a little example on how to use it (I'm not so familiar with prototypes)? i.e. just create database, set a value, get a value.