getElementsByClassName Polyfill for IE8

getElementsByClassName-polyfill.js

(function () {
  if (!document.getElementsByClassName) {
    window.Element.prototype.getElementsByClassName = document.constructor.prototype.getElementsByClassName = function (classNames) {
      classNames || (classNames = '*');
      classNames = classNames.split(' ').join('.');
      
      if (classNames !== '*') {
        classNames = '.' + classNames;
      }
      
      return this.querySelectorAll(classNames);
    };  
  }
  
})();