Function computeRelativeURL

lib/util.js:255–283

* Given two URLs that are assumed to be on the same * protocol/host/user/password build a relative URL from the * path, params, and hash values. * * @param rootURL The root URL that the target will be relative to. * @param targetURL The target that the relative URL points to. * @return A rootU

(rootURL, targetURL)

 * @return A rootURL-relative, normalized URL value.
 */
function computeRelativeURL(rootURL, targetURL) {
  if (typeof rootURL === "string") rootURL = new URL(rootURL);
  if (typeof targetURL === "string") targetURL = new URL(targetURL);

  const targetParts = targetURL.pathname.split("/");
  const rootParts = rootURL.pathname.split("/");

  // If we've got a URL path ending with a "/", we remove it since we'd
  // otherwise be relative to the wrong location.
  if (rootParts.length > 0 && !rootParts[rootParts.length - 1]) {
    rootParts.pop();
  }

  while (
    targetParts.length > 0 &&
    rootParts.length > 0 &&
    targetParts[0] === rootParts[0]
  ) {
    targetParts.shift();
    rootParts.shift();
  }

  const relativePath = rootParts
    .map(() => "..")
    .concat(targetParts)
    .join("/");

  return relativePath + targetURL.search + targetURL.hash;
}

/**
 * Given a URL, ensure that it is treated as a directory URL.