Function extname

packages/qwik/src/optimizer/src/path.ts:434–485

(path: string)

  };

  const extname = function extname(path: string) {
    assertPath(path);
    let startDot = -1;
    let startPart = 0;
    let end = -1;
    let matchedSlash = true;
    // Track the state of characters (if any) we see before our first dot and
    // after any path separator we find
    let preDotState = 0;
    for (let i = path.length - 1; i >= 0; --i) {
      const code = path.charCodeAt(i);
      if (code === 47 /*/*/) {
        // If we reached a path separator that was not part of a set of path
        // separators at the end of the string, stop now
        if (!matchedSlash) {
          startPart = i + 1;
          break;
        }
        continue;
      }
      if (end === -1) {
        // We saw the first non-path separator, mark this as the end of our
        // extension
        matchedSlash = false;
        end = i + 1;
      }
      if (code === 46 /*.*/) {
        // If this is our first dot, mark it as the start of our extension
        if (startDot === -1) {
          startDot = i;
        } else if (preDotState !== 1) {
          preDotState = 1;
        }
      } else if (startDot !== -1) {
        // We saw a non-dot and non-path separator before our dot, so we should
        // have a good chance at having a non-empty extension
        preDotState = -1;
      }
    }

    if (
      startDot === -1 ||
      end === -1 ||
      // We saw a non-dot character immediately before the dot
      preDotState === 0 ||
      // The (right-most) trimmed path component is exactly '..'
      (preDotState === 1 && startDot === end - 1 && startDot === startPart + 1)
    ) {
      return '';
    }
    return path.slice(startDot, end);
  };

  const format = function format(pathObject: FormatInputPathObject) {
    if (pathObject === null || typeof pathObject !== 'object') {