normalize_paths translated from Erlang to Javascript

normalize_path.erl

% normalize_path experiments

-define(SEPARATOR, $\/).

main(_) -> ok
    , Paths = [ ""
              , "/"
              , "/foo/bar/baz"
              , "foo/one//two///three////"
              , "foo/bar/..//baz"
              ]
    , lists:foreach(fun(Path) -> ok
        , io:format("~s => ~s\n", [Path, normalize_path(Path)])
        end, Paths)
    .

normalize_path(Path)  ->
    "/" ++ string:join(normalize_path1(string:tokens(Path,
                "/"), []), [?SEPARATOR]).


normalize_path1([], Acc) ->
    lists:reverse(Acc);
normalize_path1([".."|Rest], Acc) ->
    Acc1 = case Acc of
        [] -> [".."|Acc];
        [T|_] when T =:= ".." -> [".."|Acc];
        [_|R] -> R
    end,
    normalize_path1(Rest, Acc1);
normalize_path1(["."|Rest], Acc) ->
    normalize_path1(Rest, Acc);
normalize_path1([Path|Rest], Acc) ->
    normalize_path1(Rest, [Path|Acc]).

normalize_path.js

var SEPARATOR = '/'

main()
function main() {
  var paths = [ ""
              , "/"
              , "/foo/bar/baz"
              , "foo/one//two///three////"
              , "foo/bar/..//baz"
              ]
  paths.forEach(function(path, i) {
    console.log(path + ' => ' + normalize_path(path))
  })
}

function string_tokens(str, separator) {
  return str.split(separator).filter(function(part) { return part != '' })
}

// normalize_path(Path)  ->
function normalize_path(path) {
  return '/' + normalize_path1(string_tokens(path, '/'), []).join(SEPARATOR)
}

function normalize_path1(parts, acc) {
  // normalize_path1([], Acc) ->
  if(parts.length == 0)
    return acc.reverse()

  // normalize_path1([".."|Rest], Acc) ->
  else if(parts[0] == '..') {
    var rest = parts.slice(1)
    var acc1
    if(acc.length == 0)
      acc1 = ['..'].concat(acc)
    else if(acc[0] == '..')
      acc1 = ['..'].concat(acc)
    else
      acc1 = acc.slice(1)

    return normalize_path1(rest, acc1)
  }

  // normalize_path1(["."|Rest], Acc) ->
  else if(parts[0] == '.') {
    var rest = parts.slice[1]
    return normalize_path1(rest, acc)
  }

  // normalize_path1([Path|Rest], Acc) ->
  else {
    var path = parts[0]
      , rest = parts.slice(1)
    return normalize_path1(rest, [path].concat(acc))
  }
}

notes.md

From https://github.com/apache/couchdb/blob/master/src/couchdb/couch_httpd_rewrite.erl#L367-385

Output for both programs:

 => /
/ => /
/foo/bar/baz => /foo/bar/baz
foo/one//two///three//// => /foo/one/two/three
foo/bar/..//baz => /foo/baz