to-absolute-url.js: URL文字列を絶対URLに変換 (※DOM L2 HTML の HTMLAnchorElement#href 依存)

to-absolute-url.js

/**
 * to-absolute-url.js
 *
 * @version 1.0.1
 * @author think49
 * @url https://gist.github.com/think49/1e8944a19a36dd57c829
 * @license http://www.opensource.org/licenses/mit-license.php (The MIT License)
 */

'use strict';

var toAbsoluteUrl = (function (currentDirectory, anchorElement) {
  var toAbsoluteUrl;

  function toAbsoluteUrlByHref (url) {
    anchorElement.href = url;
    return anchorElement.href;
  }

  function toAbsoluteUrlByCloneHref (url) {
    anchorElement.href = url;
    return anchorElement.cloneNode(false).href;   // for IE6, IE7
  }

  if (toAbsoluteUrlByHref('t') === currentDirectory + 't') {
    toAbsoluteUrl = toAbsoluteUrlByHref;
  } else if (toAbsoluteUrlByCloneHref('t') === currentDirectory + 't') {
    toAbsoluteUrl = toAbsoluteUrlByCloneHref;
  } else {
    throw new Error;
  }

  return toAbsoluteUrl;
})(location.protocol + '//' + location.host + location.pathname.replace(/[^\x2f]+$/, ''), document.createElement('a'));