Define dialog arguments
<html> <body> <script language="JavaScript"> function function1() { var myArguments = new Object(); myArguments.param1 = document.all.myColor.value; window.showModalDialog("http://www.java2s.com", myArguments, ''); } </script> <select id="myColor"> <option value="red">Red</option> <option value="green">Green</option> <option value="blue">Blue</option> <option value="yellow">Yellow</option> </select> <button onclick="function1();">Open Window</button> </body> </html>