DigitalState / Formio

function pathtoRegexp(path, keys, options) {

  options = options || {};

  keys = keys || [];

  var strict = options.strict;

  var end = options.end !== false;

  var flags = options.sensitive ? '' : 'i';

  var extraOffset = 0;

  var keysOffset = keys.length;

  var i = 0;

  var name = 0;

  var m;

  if (path instanceof RegExp) {

    while (m = MATCHING_GROUP_REGEXP.exec(path.source)) {

      keys.push({

        name: name++,

        optional: false,

        offset: m.index

      });

    }

    return path;

  }

  if (Array.isArray(path)) {

    // Map array parts into regexps and return their source. We also pass

    // the same keys and options instance into every generation to get

    // consistent matching groups before we join the sources together.

    path = path.map(function (value) {

      return pathtoRegexp(value, keys, options).source;

    });

    return new RegExp('(?:' + path.join('|') + ')', flags);

  }

  path = ('^' + path + (strict ? '' : path[path.length - 1] === '/' ? '?' : '/?'))

    .replace(/\/\(/g, '/(?:')

    .replace(/([\/\.])/g, '\\$1')

    .replace(/(\\\/)?(\\\.)?:(\w+)(\(.*?\))?(\*)?(\?)?/g, function (match, slash, format, key, capture, star, optional, offset) {

      slash = slash || '';

      format = format || '';

      capture = capture || '([^\\/' + format + ']+?)';

      optional = optional || '';

      keys.push({

        name: key,

        optional: !!optional,

        offset: offset + extraOffset

      });

      var result = ''

        + (optional ? '' : slash)

        + '(?:'

        + format + (optional ? slash : '') + capture

        + (star ? '((?:[\\/' + format + '].+?)?)' : '')

        + ')'

        + optional;

      extraOffset += result.length - match.length;

      return result;

    })

    .replace(/\*/g, function (star, index) {

      var len = keys.length

      while (len-- > keysOffset && keys[len].offset > index) {

        keys[len].offset += 3; // Replacement length minus asterisk length.

      }

      return '(.*)';

    });

  // This is a workaround for handling unnamed matching groups.

  while (m = MATCHING_GROUP_REGEXP.exec(path)) {

    var escapeCount = 0;

    var index = m.index;

    while (path.charAt(--index) === '\\') {

      escapeCount++;

    }

    // It's possible to escape the bracket.

    if (escapeCount % 2 === 1) {

      continue;

    }

    if (keysOffset + i === keys.length || keys[keysOffset + i].offset > m.index) {

      keys.splice(keysOffset + i, 0, {

        name: name++, // Unnamed matching groups must be consistently linear.

        optional: false,

        offset: m.index

      });

    }

    i++;

  }

  // If the path is non-ending, match until the end or a slash.

  path += (end ? '$' : (path[path.length - 1] === '/' ? '' : '(?=\\/|$)'));

  return new RegExp(path, flags);

};