JavaScript break 语句

<html>
   <body>
      <script>
         var x = 1;
         document.write("Entering the loop <br/> ");

         while (x < 20) {
            if (x == 5) {
               break; // breaks out of loop completely
            }
            x = x +1;
            document.write( x + "<br/>");
         }
      </script>
   </body>
</html>