title: Isotope JS Error
body: <p>Need a bit of help with a Js error I am getting please:</p>
  
  <blockquote>
    <p>Uncaught TypeError: $portfolio.isotope is not a function</p>
  </blockquote>
  
  <pre>  
  //ISOTOPE FUNCTION - FILTER PORTFOLIO FUNCTION
  
      $portfolio = $('.portfolio-items');
      $portfolio.isotope({
          itemSelector : 'li',
          layoutMode : 'fitRows'
      });
      $portfolio_selectors = $('.portfolio-filter >li>a');
      $portfolio_selectors.on('click', function(){
          $portfolio_selectors.removeClass('active');
          $(this).addClass('active');
          var selector = $(this).attr('data-filter');
          $portfolio.isotope({ filter: selector });
          return false;
      });
  </pre>