Normalize IE's createStyleSheet

document.createStyleSheet.js

if ( typeof document.createStyleSheet !== 'function' ) {
  document.createStyleSheet = function(url, index) {
    var styleElement;
    if ( typeof url === 'string' ) {
      styleElement = document.createElement('style');
      if ( url.replace('{', '') !== url ) {
        if ( styleElement.styleSheet ) {
          styleElement.styleSheet.cssText = url;
        } else {
          styleElement.appendChild(document.createTextNode(url));
        }
      } else {
        styleElement      = document.createElement('link');
        styleElement.rel  = 'stylesheet';
        styleElement.href = url;
      }
    } else {
      styleElement = document.createElement('style');
    }
    styleElement.type = 'text/css';
    if ( typeof index === 'number' ) {
      if ( index > document.styleSheets.length - 1 ) {
        index = document.styleSheets.length - 1;
      }
      if ( index < 0 ) {
        index = 0;
      }
      var styleSheetTag = document.styleSheets[index].ownerNode;
      styleSheetTag.parentNode.insertBefore(styleElement, styleSheetTag);
    } else {
      document.getElementsByTagName('head')[0].appendChild(styleElement);
      index = document.styleSheets.length - 1;
    }
    try {
      if ( !('addRule' in CSSStyleSheet.prototype) && typeof CSSStyleSheet.prototype.insertRule === 'function' ) {
        CSSStyleSheet.prototype.addRule = function(selector, rule) {
          this.insertRule(selector + '{ '+ rule + '}', this.cssRules.length);
        };
      }
    } catch (e) {}
    return document.styleSheets[index];
  };
}