javascript - submit form data in html and send to server -

<form id="myform"><label for="name">username:</label> <input type="text" id="username" name="username"> <button id= "btnsub" onclick="registeruser();">register</button></form> <script>  var url="http://localhost/rrrr/register.php?username="+ username; var username ;       function registeruser() {            document.getelementbyid("myform").action=url;           alert("btn click") ;           alert(username+''); } </script> 

i tried above code, button click displays alert box undefined problem ?

if use username directly treated javascript variable not defined. getting value of username input element.

you have use this

var username = document.getelementbyid('username').value; var url="http://localhost/rrrr/register.php?username="+ username;  function registeruser() {            document.getelementbyid("myform").action=url;           alert("btn click") ;           alert(username+''); } 

for submitting form can this

document.getelementbyid("myform").submit(); 

try this

<form><label for="name">username:</label> <input type="text" id="username" name="username"> <script>  var username = document.getelementbyid('username').value; var url="http://localhost/rrrr/register.php?username="+ username;  function registeruser() {            document.getelementbyid("myform").action=url;           alert("btn click") ;           alert(username+''); document.getelementbyid("myform").submit(); } </script> <button id= "btnsub" onclick="registeruser();">register</button></form>