Gives the ability to get an absolute URL from a relative URL and an absolute base URL.

getAbsUrl.js

function getAbsUrl(relUrl, baseUrl) {
  // Make sure baseUrl ends in a forward-slash
  baseUrl = baseUrl.replace(/^(\w*\:\/\/[^\/\?]+)([\?#]|$)/, '$1/$2');

  var firstChar = relUrl.charAt(0);
  if (firstChar === '?') {
    return baseUrl.replace(/[\?#].*$|$/, relUrl);
  }
  if (firstChar === '#') {
    return baseUrl.replace(/#.*$|$/, relUrl);
  }
  if (firstChar === '/') {
    return baseUrl.replace(/^(\w+:\/\/[^\/]+)\/.*/, '$1') + relUrl;
  }
  
  for (
    relUrl = baseUrl.replace(/\/[^\/\?#]*([#\?].*)?$/, '/') + relUrl;
    baseUrl = relUrl.replace(/(^[^\?#]+[^\/]\/)(?!\.\.\/)[^\/]+\/\.\.\//, '$1'), baseUrl !== relUrl;
    relUrl = baseUrl
  );
  return relUrl.replace(/(^\w+:\/\/[^\/]+\/)(?:\.\.\/)+/, '$1');
}