code: function PersistentStorage(namespace, override) {
    this.prefix = ['__', namespace, '__'].join('');
    this.ttlKey = '__ttl__';
    this.keyMatcher = new RegExp('^' + _.escapeRegExChars(this.prefix));
  
    // for testing purpose
    this.ls = override || LOCAL_STORAGE;
  
    // if local storage isn't available, everything becomes a noop
    !this.ls && this._noop();
  }
docs: constructor -----------