title: run part of an event once and run other part several times
body: <pre><code>$(".a").on("click",function(){
          $("b").stop(true, true).slideUp(500);
          $(this).next("c").stop(true, true).slideDown(500);
      });
  </code></pre>
  
  <p>I want when user clicks "a", this line (line 1) run only once:</p>
  
  <pre><code>$("b").stop(true, true).slideUp(500);
  </code></pre>
  
  <p>but this line (line 2) run unlimited:</p>
  
  <pre><code>$(this).next("c").stop(true, true).slideDown(500);
  </code></pre>
  
  <p>Thats mean, when user clicks "a" again, line 1 not run but line 2 be run.
  How? I try this but not work:</p>
  
  <pre><code>$(".a").on("click",function(event){
              $("b").stop(true, true).slideUp(500);
              $(this).next("c").stop(true, true).slideDown(500);
              $(this).off( event );
          });
  </code></pre>