how to add javascript validation in jsp

Question

I have a javascript file in web/js/Validation.js directory. In my Login.jsp, I am calling this .js file to validate username. This does not seem to be working, please can you help.

I've tried using src="/js/Validation.js" and even changing script tag location (ie. between html and head tags) without any luck.

thanks.

Validation.js

    function simple_Validation()
    {

    var valid = true;

    if (document.login_form.user.value.lenght == 0)
    {
     alert ("Pleaes type username"); 

      valid = false;
    }

    return valid;
    }

Login.jsp

    <%@ page language="java" contentType="text/html; charset=ISO-8859-1"
        pageEncoding="ISO-8859-1"%>
    <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
    <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
    <%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn"%>
    <html>
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
    <script type="text/javascript" src="js/Validation.js">

    </script>

    <title>Login</title>

    </head>
    <body>

        <form name="login_form" action="LoginServlet" method="post"
            onSubmit="return simple_Validation();">
            <table border="0">
                <tr align="left" valign="top">
                    <td>User Name:</td>
                    <td><input type="text" name="user" class="inputbox" /></td>
                </tr>
                <tr align="left" valign="top">
                    <td>Password:</td>
                    <td><input type="password" name="pass" class="inputbox" /></td>
                </tr>
                <tr align="left" valign="top">
                    <td></td>
                    <td><input type="submit" name="submit" value="Login" /></td>
                </tr>
            </table>
            <c:out value="${loginresult}">
            </c:out>

        </form>
    </body>
    </html>

Did you try alerting something inside of the function to make sure the JS file is referenced correctly and the function is being called? If you can confirm it's being called, then it's problem the spelling problem that @marteljn noticed — Ian
– Ian, Commented Sep 16, 2012 at 15:54
Is your JS file being loaded? E.g. do you see a 404 for that file in Firebug (or Chrome inspector, etc)? If not then its a JS issue, what output do your see in Firebug/Chrome console output? — nickdos
– nickdos, Commented Sep 17, 2012 at 0:56
thanks for your response Guys. Yes, the problem was with my spellings. — Muhammad
– Muhammad, Commented Sep 18, 2012 at 12:21

Community · Accepted Answer · 2017-05-23 12:03:18Z

1

We have come a long way in javascript technology and we have a lot of tools to debug javascript (unlike putting a lot of alerts, though I think this is by far the simplest and best ;-)) which are easy to use and guess what? Some are free!

So one such tool (probably one of the best) is firebug which comes as an add-on for firefox.

chrome, ie9 & safari has some built-in developer tools, they appear when you press F12 on your PC (on Mac I am not sure :-))

So here are some steps:

Install Firefox
Install firebug
Load your page
Enable firebug for your page. Enable scripting panel
Reload your page
Check if the file is loaded properly (taken from nickdos's comment)
Check if there is some javascript error (probably the spelling of length taken from marteljn's comment)

edited May 23, 2017 at 12:03

CommunityBot

11 silver badge

answered Sep 17, 2012 at 8:17

Prakash K

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Comments

Bijoyendra Deb Roy · Accepted Answer · 2013-12-12 09:20:16Z

0

in your javascript you have mispelled length as lenght.

answered Dec 12, 2013 at 9:20

Bijoyendra Deb Roy

1

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