join.ts

/**
 * Same as joinPath, but preserves http(s):// schemes
 *
 * @param segments Url segments to join
 * @return Joined url
 */
function joinUrl(...segments: string[]): string {
  if (segments.length === 0) {
    return "";
  }
  let first   = segments[0],
      rest    = segments.slice(1),
      schemes = /^(http|https):\/\//,
      match   = schemes.exec(first),
      prefix  = match ? match[0] : "";
  first = first.slice(prefix.length);
  return prefix + joinPath(first, ...rest);
}

/**
 * Joins path segments.  Preserves initial "/" and resolves ".." and "."
 * Does not support using ".." to go above/outside the root.
 * This means that join("foo", "../../bar") will not resolve to "../bar"
 *
 * @param segments Path segments to join
 * @return Joined path
 */
function joinPath(...segments: string[]): string {
  let parts: string[] = [];
  for (let segment of segments) {
    parts = parts.concat(segment.toString().split("/"));
  }
  let newParts: string[] = [];
  for (let part of parts) {
    if (!part || part === ".") {
      continue;
    }
    if (part === "..") {
      newParts.pop();
    } else {
      newParts.push(part);
    }
  }
  // Preserve the initial slash if there was one.
  if (parts[0] === "") newParts.unshift("");
  // Turn back into a single string path.
  return newParts.join("/") || (newParts.length ? "/" : ".");
}