title: What if I use "throw" in "catch"?
body: <pre><code>function f(){
      try{
          if (/*some codes*/) throw false;
          return true;
      }
      catch(x){
          if (x===false) return false;
          throw x;
      }
  }
  </code></pre>
  
  <p>Here,what does "throw x" mean? It seems codes in "catch" won't run twice.</p>