Javascript Object compact()

// Compact (object)
// ----------------
// Removes falsy values/keys
Object.prototype.compact = function() {
  var key, compacted;
  compacted = {};//from  www .  ja  v  a  2s. c o m
  for(key in this) {
    if(this[key]) {
      compacted[key] = this[key];
    }
  }
  return compacted;
}