docs: function arrayToDict(array, valueToKeyFn, opt_this) {
      opt_this = opt_this || this;
      var result = {};
      var length = array.length;
      for (var i = 0; i < length; i++) {
        var value = array[i];
        var key = valueToKeyFn.call(opt_this, value);
        result[key] = value;
      }
      return result;
    }