Only after something is typed inside the textbox, The button should be enabled.

Copy the following code in the notepad and save it as test.htm and then run it.
<form name="form1"> <input type="text" name="iserod" id="userid" onKeyUp="enableBn1();"/> <input id="button1" type="button" disabled="disabled" value="Button1"> </form> <script> function enableBn1(){ if(document.form1.userid == ""){ document.form1.button1.disabled = true; } else{ document.form1.button1.disabled = false; } } </script>

Ajax code for Check Availability of User ID

<form name="form1"> <input type="text" name="userid" id="userid" /> <input id="button1" type="button" value="check availability" onclick="sendLamens();"> </form> <div id="label1"></div> <script> function sendLamens(){ if(window.XMLHttpRequest) { lamens = new XMLHttpRequest(); } else if(window.ActiveXObject){ lamens = new ActiveXObject("Microsoft.XMLHTTP"); } lamens.open("POST", "test1.asp", true); lamens.onreadystatechange = fetchFromLamens; lamens.setRequestHeader("Content-Type", "application/x-www-form-urlencoded"); lamens.send("userid=" + document.form1.userid.value); } function fetchFromLamens(){ if(lamens.readyState == 4){ if(lamens.status == 200){ document.getElementById("label1").innerHTML = lamens.responseText; } else{ document.getElementById("label1").innerHTML = "error"; } } } </script>

The Textbox should accept ONLY NUMBERS

The Textbox should accept ONLY UPPER CASE
Show The Code

What is the newline character for alert message?

< script language="Javascript" >
   alert("Hello\r\nMy Name is Preity");
< /script >

Note : In some browsers "\n" will work and some browers "\r\n" will work. For a safer side, always use "\r\n". Here r-stands for return, n-stands for new line. .

Lamens Javascript

Only after something is typed inside the textbox, The button should be enabled.

Ajax code for Check Availability of User ID