Function dirname

lib/path.js:803–892

* @param {string} path * @returns {string}

(path)

   * @returns {string}
   */
  dirname(path) {
    validateString(path, 'path');
    const len = path.length;
    if (len === 0)
      return '.';
    let rootEnd = -1;
    let offset = 0;
    const code = StringPrototypeCharCodeAt(path, 0);

    if (len === 1) {
      // `path` contains just a path separator, exit early to avoid
      // unnecessary work or a dot.
      return isPathSeparator(code) ? path : '.';
    }

    // Try to match a root
    if (isPathSeparator(code)) {
      // Possible UNC root

      rootEnd = offset = 1;

      if (isPathSeparator(StringPrototypeCharCodeAt(path, 1))) {
        // Matched double path separator at beginning
        let j = 2;
        let last = j;
        // Match 1 or more non-path separators
        while (j < len &&
               !isPathSeparator(StringPrototypeCharCodeAt(path, j))) {
          j++;
        }
        if (j < len && j !== last) {
          // Matched!
          last = j;
          // Match 1 or more path separators
          while (j < len &&
                 isPathSeparator(StringPrototypeCharCodeAt(path, j))) {
            j++;
          }
          if (j < len && j !== last) {
            // Matched!
            last = j;
            // Match 1 or more non-path separators
            while (j < len &&
                   !isPathSeparator(StringPrototypeCharCodeAt(path, j))) {
              j++;
            }
            if (j === len) {
              // We matched a UNC root only
              return path;
            }
            if (j !== last) {
              // We matched a UNC root with leftovers

              // Offset by 1 to include the separator after the UNC root to
              // treat it as a "normal root" on top of a (UNC) root
              rootEnd = offset = j + 1;
            }
          }