code: function boolean(value) {
    var parsedBoolean = json(value);
  
    // handle 0|1 case
    if (typeOf(parsedBoolean) == 'number' && [0, 1].indexOf(parsedBoolean) > -1) {
      parsedBoolean = parsedBoolean === 0 ? false : true;
    }
  
    // couldn't parse it
    if (typeOf(parsedBoolean) != 'boolean') {
      return throwModifierError('boolean', value, {message: 'Invalid Boolean'});
    }
  
    return parsedBoolean;
  }
docs: Parses provided string as a boolean (json + boolean validation)
  
  @param   {string} value - string to parse
  @returns {boolean} - Parsed boolean