javascript setTimeout

<script src=jq.js></script>
 <script>  
 function p1(){   
             $("#test").show(); 
          }     
 function p2(){ 
        p1();       
  setTimeout("p3()",1000)   
  }      
 
 function p3(){     
  $("#test").hide();    
  }     
 function p4(){     
             p2();           
   } </script> 
 <button onClick="p4()">测试</button>  <div id='test' style="display:none">loading..</div