JavaScript void undefined 空值

JavaScript void undefined 空值

<html>
   <head>

      <script type = "text/javascript">
         <!--
            function getValue() {
               var a,b,c;

               a = void ( b = 5, c = 7 );
               document.write('a = ' + a + ' b = ' + b +' c = ' + c );
            }
         //-->
      </script>

   </head>

   <body>
      <p>Click the following to see the result:</p>

      <form>
         <input type = "button" value = "Click Me" onclick = "getValue();" />
      </form>

   </body>
</html>