function realpath (path) {
  // http://kevin.vanzonneveld.net
  // +   original by: mk.keck
  // +   improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // %        note 1: Returned path is an url like e.g. 'http://yourhost.tld/path/'
  // *     example 1: realpath('../.././_supporters/pj_test_supportfile_1.htm');
  // *     returns 1: 'file:/home/kevin/workspace/_supporters/pj_test_supportfile_1.htm'
  var p = 0,
    arr = []; /* Save the root, if not given */
  var r = this.window.location.href; /* Avoid input failures */
  path = (path + '').replace('\\', '/'); /* Check if there's a port in path (like 'http://') */
  if (path.indexOf('://') !== -1) {
    p = 1;
  } /* Ok, there's not a port in path, so let's take the root */
  if (!p) {
    path = r.substring(0, r.lastIndexOf('/') + 1) + path;
  } /* Explode the given path into it's parts */
  arr = path.split('/'); /* The path is an array now */
  path = []; /* Foreach part make a check */
  for (var k in arr) { /* This is'nt really interesting */
    if (arr[k] == '.') {
      continue;
    } /* This reduces the realpath */
    if (arr[k] == '..') {
/* But only if there more than 3 parts in the path-array.
       * The first three parts are for the uri */
      if (path.length > 3) {
        path.pop();
      }
    } /* This adds parts to the realpath */
    else {
/* But only if the part is not empty or the uri
       * (the first three parts ar needed) was not
       * saved */
      if ((path.length < 2) || (arr[k] !== '')) {
        path.push(arr[k]);
      }
    }
  } /* Returns the absloute path as a string */
  return path.join('/');
}

realpath('../.././_supporters/pj_test_supportfile_1.htm');

'file:/home/kevin/workspace/_supporters/pj_test_supportfile_1.htm'