checks if an element has a class(s)

DOM - hasClass

Element.prototype.hasClass = Element.prototype.hasClass || 
  function(classArr){
    var hasClass = 0,
        className = this.getAttribute('class');
  
    if( this == null || !classArr || !className ) return false;
  
    if( !(classArr instanceof Array) )
      classArr = classArr.split(' ');

    for( var i in classArr )
      // this.classList.contains(classArr[i]) // for modern browsers
      if( className.split(classArr[i]).length > 1 )  
          hasClass++;

    return hasClass == classArr.length;
};