code: function processScalarParam(existedParam: Object, value: Object): Object {
    if (Array.isArray(existedParam)) {
      // value is already an array, so push on the next value.
      existedParam.push(value);
      return existedParam;
    }
    if (existedParam !== undefined) {
      // value isn't an array, but since a second value has been specified,
      // convert value into an array.
      return [existedParam, value];
    }
    // value is a scalar.
    return value;
  }
docs: Process parameter that was recognized as scalar param (primitive value or shallow array).
  
  @param existedParam Object with previously parsed values for specified key.
  @param value Parameter value to append.
  @returns Initial primitive value or transformed existedParam if parameter was recognized as an array.