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Detect Caps Lock with JavaScript

, 16 Jan 2007 CPOL
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How to detect CapsLock with Javascript.


I'm sure that this script will help you in some of your projects that needs a username and password.

Sometimes when we want access to a secure page that asks for a username and password and we submit the information but we didn't know that the password was submitted in upper case, we get an error.


We can avoid this kind of problems by just adding some JavaScript code to our page.

Building the script

<script language="Javascript">
function capLock(e){
 kc = e.keyCode?e.keyCode:e.which;
 sk = e.shiftKey?e.shiftKey:((kc == 16)?true:false);
 if(((kc >= 65 && kc <= 90) && !sk)||((kc >= 97 && kc <= 122) && sk))
  document.getElementById('divMayus').style.visibility = 'visible';
  document.getElementById('divMayus').style.visibility = 'hidden';

Now we have our script ready to go. We now need to associate this script with our form.

Using the script

Let's add two items: a textbox and a DIV. Now we just need to call the onKeyPress event.

<input type="password" name="txtPassword" onkeypress="capLock(event)" />
<div id="divMayus" style="visibility:hidden">Caps Lock is on.</div> 

See if it works on your project.


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Web Developer Softtek GDC Ensenada
Mexico Mexico
No Biography provided

Comments and Discussions

QuestionIE-Onkeypress Pinmembertpkpradeep27-Dec-12 0:51 
GeneralMy vote of 4 PinmemberThe nk5-Oct-11 2:32 
GeneralMy vote of 5 Pinmembersivakumar32126-May-11 3:48 
Generalthanks PinmemberAkash442-Sep-10 19:16 
Generalrealy helpful PinmemberAbhijit Jana10-Jun-08 5:05 
QuestionWhy? PinmemberDomingo M. Asuncion13-Mar-07 17:11 
GeneralReally nice. Pinmemberumasankar312-Mar-07 18:34 
GeneralNice but.. Pinmemberparadoxxl17-Feb-07 23:59 
QuestionIt doesn't work in IE6? Pinmemberbencalie30-Jan-07 15:10 
QuestionHow about non a-z characters? PinmemberStaffan (xtaff) Sjöstedt22-Jan-07 23:22 
Thank you for pointing out this solution.
However, I have, along with a lot of others I think, problem with characters like äöå (I'm Swedish). The script does not react since they have a key code greater than 122.
So I suggest the following instead: Check if the last typed character is changed when transformed to lower/upper case depending on the shift key.
To achieve this we need to respond to onkeyup instead of onkeypress, because otherwise the input element will not have received the character yet.
So my suggestion goes like this:
     function capLock(e){
     if( !e )
          e = window.event;
     kc = e.keyCode?e.keyCode:e.which;
     sk = e.shiftKey?e.shiftKeyCry | :(( kc == 16)?true:false);
     // get the src element
     var src = e.srcElement ? e.srcElement :;
     // get the last character
     var c = src.value.substr( src.value.length-1,1 );
     // check upper/Lower case
     if(   c != c.toLowerCase() && !sk || c != c.toUpperCase() && sk )
        document.getElementById('divMayus').style.visibility = 'visible';
        document.getElementById('divMayus').style.visibility = 'hidden';

<input type="password" name="txtPassword" onkeyup="capLock(event)" />
<div id="divMayus" >Caps Lock is on.</div>

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