Código HTML:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <html> <head> <title>formularios - creación de menús - ejemplo 4</title> </head> <body> <form name="doublecombo"> <p><select name="example" size="1" onChange="redirect(this.options.selectedIndex)"> <option>Tecnología</option> <option>Noticias</option> <option>Buscadores</option> </select> <select name="stage2" size="1"> <option value="http://wsabstract.com">Website Abstraction</option> <option value="http://www.news.com">News.com</option> <option value="http://www.wired.com">Wired News</option> </select> <input type="button" name="test" value="visitar" onClick="go()"> </p> <script> <!-- var groups=document.doublecombo.example.options.length var group=new Array(groups) for (i=0; i<groups; i++) group[i]=new Array() group[0][0]=new Option("Website Abstraction","http://wsabstract.com") group[0][1]=new Option("News.com","http://www.news.com") group[0][2]=new Option("Wired News","http://www.wired.com") group[1][0]=new Option("CNN","http://www.cnn.com") group[1][1]=new Option("ABC News","http://www.abcnews.com") group[2][0]=new Option("Hotbot","http://www.hotbot.com") group[2][1]=new Option("Infoseek","http://www.infoseek.com") group[2][2]=new Option("Excite","http://www.excite.com") group[2][3]=new Option("Lycos","http://www.lycos.com") var temp=document.doublecombo.stage2 function redirect(x){ for (m=temp.options.length-1;m>0;m--) temp.options[m]=null for (i=0;i<group[x].length;i++){ temp.options[i]=new Option(group[x][i].text,group[x][i].value) } temp.options[0].selected=true } function go(){ location=temp.options[temp.selectedIndex].value } //--> </script> </form> </body> </html>