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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

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Comments and Discussions

SuggestionShould show message on caps lock change Pin
Arkadeep De3-Apr-15 8:16
professionalArkadeep De3-Apr-15 8:16 
QuestionIE-Onkeypress Pin
tpkpradeep27-Dec-12 0:51
membertpkpradeep27-Dec-12 0:51 
GeneralMy vote of 4 Pin
The nk5-Oct-11 2:32
memberThe nk5-Oct-11 2:32 
GeneralMy vote of 5 Pin
sivakumar32126-May-11 3:48
membersivakumar32126-May-11 3:48 
Generalthanks Pin
Akash442-Sep-10 19:16
memberAkash442-Sep-10 19:16 
Generalrealy helpful Pin
Abhijit Jana10-Jun-08 5:05
memberAbhijit Jana10-Jun-08 5:05 
QuestionWhy? Pin
Domingo M. Asuncion13-Mar-07 17:11
memberDomingo M. Asuncion13-Mar-07 17:11 
GeneralReally nice. Pin
umasankar312-Mar-07 18:34
memberumasankar312-Mar-07 18:34 
GeneralNice but.. Pin
paradoxxl17-Feb-07 23:59
memberparadoxxl17-Feb-07 23:59 
QuestionIt doesn't work in IE6? Pin
bencalie30-Jan-07 15:10
memberbencalie30-Jan-07 15:10 
The layer "divMayus" will show even the CapsLock is off. My browser is MS IE 6.

So this is my way to solve this problem. But if I just use the Number Key, the script is error. Fortunately, no matter the CapsLock is on or off, the number is the same.

function capLock(){
kc = event.srcElement.value;
document.getElementById('divMayus').style.visibility = 'visible';
document.getElementById('divMayus').style.visibility = 'hidden';
<input type="test" name="txtPassword" />

QuestionHow about non a-z characters? Pin
Staffan (xtaff) Sjöstedt22-Jan-07 23:22
memberStaffan (xtaff) Sjöstedt22-Jan-07 23:22 
AnswerRe: How about non a-z characters? Pin
astanton19787-Mar-08 7:02
memberastanton19787-Mar-08 7:02 

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