var menuLeft = document.getElementById( 'cbp-spmenu-s1' ),
  	  showLeftPush = document.getElementById( 'showLeftPush' ),
      body = document.body;

  showLeftPush.onclick = function() {
      classie.toggle( this, 'active' );
      classie.toggle( body, 'cbp-spmenu-push-toright' );
      classie.toggle( menuLeft, 'cbp-spmenu-open' );
  };