Getting the value from a prompt box

Hello I'm trying to make a simple web chat, and I want the user to choose his name when he first load the chat page and for this I'm using this function:

function Login(un)
{
var x=prompt("Please enter your name","");
var xmlhttp;
if (window.XMLHttpRequest)
  {// Използваните браузъри
  xmlhttp=new XMLHttpRequest();
  }
else
  {// Кой ли ползва тези версии..
  xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
  }
    xmlhttp.open("GET","login.php?u="+un,true);
    xmlhttp.send();
}

I put this in the head section and then in the body onload... I call the function but can't figure out how to extract the text from the prompt box.I tried

login(getElementsByName('x').开发者_开发百科value)

But obvously that's not the way, so, please help. Thanks Leron

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var x=prompt("Please enter your name","");

Then x has the value entered in the prompt.

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var login = getElementsByName('loginboxname').value;

Just make sure you replace "loginboxname" with the actual name of your login box. The variable "login" should then the value of that box.