Hello everyone quick question.
First time working with java script
I have a jsp file that will create a data grid and one of the columns of the data grid are checkboxes. My question is can a JSP file contain javascript in it or will I have to create a different file for just the javascript. The function of the java script will be a select all button.
If JSP can hold javascript where does the code belong? by this I mean what headers does the code reside int?
<html>
Thanks for the help everyone.
I've just answered a similar question here:
https://stackoverflow.com/questions/25059168/java-websocket-client-in-jsp-possible/25059382#25059382
The generic answer is: JSP can contain anything that a regular HTML page can contain. JSP is an HTML extended with JSP tags that are processed on a server. After the JSP tags are processed and a response is generated there is no any difference between that response and a regular HTML.
So, the question really is where to store the java scripts in an HTML. I think, the cleanest way would be to put them to a separate file or files and then use a <script> tag with an 'src' attribute:
<script src="<java-script-url>"></script>
But in cases when java scripts are not that big and complicated, it's OK to include them to the page itself under <head> element of your page.
Script tags should be added under the head tag of the HTML node.
The script tag can then simply contain JavaScript.
This should not be any different from adding a script tag to a normal html page.
<html>
<head>
<script type="text/javascript"><!-- required for FF3 and Opera --><jsp:text> </jsp:text></script>
</head>
</html>
Add inline javascript to the body of the jsp:text (jsp:text may not be necessary, I am not sure), or add a src="" attribute containing the path relative (or absolute) to the URL the browser will consume the page from.
Yes, it technically can. You'd simply put it under a <script> tag inside <head>. However, I recommend including a JavaScript file using a <script> tag, instead of inserting JavaScript directly into your JSP.
There is no dependency between JavaScript and JSP because JavaScript is used for client side scripting and JSP is used to produce HTML pages or contents dynamically using Java EE. JavaScript can be used along with HTML on any browser that supports JavaScript (all browsers we use for work and development supports JavaScript).
Feel free to write JavaScript functions and code for HTML page to create an interactive website, it doesn't matter whether you are using ASP, JSP or PHP for server side scripting and dynamic HTML content generation because all these frameworks produce and use HTML, CSS, JavaScript and Media Contents. Your browser can only understand HTML, CSS and JavaScript, its the web server application which understands JSP and its Java code.
Why don't you write this code in your JSP page and check yourself whether it works or not.
<script type="text/javascript">alert('Hello World!');</script>
JavaScript is not limited to be written inside <head> tag, you can write it anywhere you want in a HTML page. There are some cases in which you would like to write a JavaScript function at the end of <body> tag.
There was a post this morning asking about how many people disable JavaScript. Then I began to wonder what techniques might be used to determine if the user has it disabled.
Does anyone know of some short/simple ways to detect if JavaScript is disabled? My intention is to give a warning that the site is not able to function properly without the browser having JS enabled.
Eventually I would want to redirect them to content that is able to work in the absence of JS, but I need this detection as a placeholder to start.
I'd like to add my .02 here. It's not 100% bulletproof, but I think it's good enough.
The problem, for me, with the preferred example of putting up some sort of "this site doesn't work so well without Javascript" message is that you then need to make sure that your site works okay without Javascript. And once you've started down that road, then you start realizing that the site should be bulletproof with JS turned off, and that's a whole big chunk of additional work.
So, what you really want is a "redirection" to a page that says "turn on JS, silly". But, of course, you can't reliably do meta redirections. So, here's the suggestion:
<noscript>
<style type="text/css">
.pagecontainer {display:none;}
</style>
<div class="noscriptmsg">
You don't have javascript enabled. Good luck with that.
</div>
</noscript>
...where all of the content in your site is wrapped with a div of class "pagecontainer". The CSS inside the noscript tag will then hide all of your page content, and instead display whatever "no JS" message you want to show. This is actually what Gmail appears to do...and if it's good enough for Google, it's good enough for my little site.
I assume you're trying to decide whether or not to deliver JavaScript-enhanced content. The best implementations degrade cleanly, so that the site will still operate without JavaScript. I also assume that you mean server-side detection, rather than using the <noscript> element for an unexplained reason.
There is no good way to perform server-side JavaScript detection. As an alternative it is possible to set a cookie using JavaScript, and then test for that cookie using server-side scripting upon subsequent page views. However this would be unsuitable for deciding what content to deliver, as it would not distinguish visitors without the cookie from new visitors or from visitors who did not accept the JavaScript set cookie.
noscript blocks are executed when JavaScript is disabled, and are typically used to display alternative content to that you've generated in JavaScript, e.g.
<script type="javascript">
... construction of ajaxy-link, setting of "js-enabled" cookie flag, etc..
</script>
<noscript>
Next Page
</noscript>
Users without js will get the next_page link - you can add parameters here so that you know on the next page whether they've come via a JS/non-JS link, or attempt to set a cookie via JS, the absence of which implies JS is disabled. Both of these examples are fairly trivial and open to manipulation, but you get the idea.
If you want a purely statistical idea of how many of your users have javascript disabled, you could do something like:
<noscript>
<img src="no_js.gif" alt="Javascript not enabled" />
</noscript>
then check your access logs to see how many times this image has been hit. A slightly crude solution, but it'll give you a good idea percentage-wise for your user base.
The above approach (image tracking) won't work well for text-only browsers or those that don't support js at all, so if your userbase swings primarily towards that area, this mightn't be the best approach.
This is what worked for me: it redirects a visitor if javascript is disabled
<noscript><meta http-equiv="refresh" content="0; url=whatyouwant.html" /></noscript>
I'd suggest you go the other way around by writing unobtrusive JavaScript.
Make the features of your project work for users with JavaScript disabled, and when you're done, implement your JavaScript UI-enhancements.
https://en.wikipedia.org/wiki/Unobtrusive_JavaScript
If your use case is that you have a form (e.g., a login form) and your server-side script needs to know if the user has JavaScript enabled, you can do something like this:
<form onsubmit="this.js_enabled.value=1;return true;">
<input type="hidden" name="js_enabled" value="0">
<input type="submit" value="go">
</form>
This will change the value of js_enabled to 1 before submitting the form. If your server-side script gets a 0, no JS. If it gets a 1, JS!
<noscript> isn't even necessary, and not to mention not supported in XHTML.
Working Example:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Frameset//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd">
<html>
<head>
<title>My website</title>
<style>
#site {
display: none;
}
</style>
<script src="http://code.jquery.com/jquery-latest.min.js "></script>
<script>
$(document).ready(function() {
$("#noJS").hide();
$("#site").show();
});
</script>
</head>
<body>
<div id="noJS">Please enable JavaScript...</div>
<div id="site">JavaScript dependent content here...</div>
</body>
</html>
In this example, if JavaScript is enabled, then you see the site. If not, then you see the "Please enable JavaScript" message. The best way to test if JavaScript is enabled, is to simply try and use JavaScript! If it works, it's enabled, if not, then it's not...
Use a .no-js class on the body and create non javascript styles based on .no-js parent class.
If javascript is disabled you will get all the non javascript styles,
if there is JS support the .no-js class will be replaced giving you all the styles as usual.
document.body.className = document.body.className.replace("no-js","js");
trick used in HTML5 boilerplate http://html5boilerplate.com/ through modernizr but you can use one line of javascript to replace the classes
noscript tags are okay but why have extra stuff in your html when it can be done with css
just a bit tough but (hairbo gave me the idea)
CSS:
.pagecontainer {
display: none;
}
JS:
function load() {
document.getElementById('noscriptmsg').style.display = "none";
document.getElementById('load').style.display = "block";
/* rest of js*/
}
HTML:
<body onload="load();">
<div class="pagecontainer" id="load">
Page loading....
</div>
<div id="noscriptmsg">
You don't have javascript enabled. Good luck with that.
</div>
</body>
would work in any case right?
even if the noscript tag is unsupported (only some css required)
any one knows a non css solution?
You can use a simple JS snippet to set the value of a hidden field. When posted back you know if JS was enabled or not.
Or you can try to open a popup window that you close rapidly (but that might be visible).
Also you have the NOSCRIPT tag that you can use to show text for browsers with JS disabled.
You'll want to take a look at the noscript tag.
<script type="text/javascript">
...some javascript script to insert data...
</script>
<noscript>
<p>Access the data.</p>
</noscript>
Because I always want to give the browser something worthwhile to look at I often use this trick:
First, any portion of a page that needs JavaScript to run properly (including passive HTML elements that get modified through getElementById calls etc.) are designed to be usable as-is with the assumption that there ISN'T javaScript available. (designed as if it wasn't there)
Any elements that would require JavaScript, I place inside a tag something like:
<span name="jsOnly" style="display: none;"></span>
Then at the beginning of my document, I use .onload or document.ready within a loop of getElementsByName('jsOnly') to set the .style.display = ""; turning the JS dependent elements back on. That way, non-JS browsers don't ever have to see the JS dependent portions of the site, and if they have it, it appears immediately when it's ready.
Once you are used to this method, it's fairly easy to hybridize your code to handle both situations, although I am only now experimenting with the noscript tag and expect it will have some additional advantages.
The noscript tag works well, but will require each additional page request to continue serving useless JS files, since essentially noscript is a client side check.
You could set a cookie with JS, but as someone else pointed out, this could fail. Ideally, you'd like to be able to detect JS client side, and without using cookies, set a session server side for that user that indicates is JS is enabled.
A possibility is to dynamically add a 1x1 image using JavaScript where the src attribute is actually a server side script. All this script does is saves to the current user session that JS is enabled ($_SESSION['js_enabled']). You can then output a 1x1 blank image back to the browser. The script won't run for users who have JS disabled, and hence the $_SESSION['js_enabled'] won't be set. Then for further pages served to this user, you can decide whether to include all of your external JS files, but you'll always want to include the check, since some of your users might be using the NoScript Firefox add-on or have JS disabled temporarily for some other reason.
You'll probably want to include this check somewhere close to the end of your page so that the additional HTTP request doesn't slow down the rendering of your page.
Add this to the HEAD tag of each page.
<noscript>
<meta http-equiv="refresh" runat="server" id="mtaJSCheck" content="0;logon.aspx" />
</noscript>
So you have:
<head>
<noscript>
<meta http-equiv="refresh" runat="server" id="mtaJSCheck" content="0;logon.aspx" />
</noscript>
</head>
With thanks to Jay.
A common solution is to the meta tag in conjunction with noscript to refresh the page and notify the server when JavaScript is disabled, like this:
<!DOCTYPE html>
<html lang="en">
<head>
<noscript>
<meta http-equiv="refresh" content="0; /?javascript=false">
</noscript>
<meta charset="UTF-8"/>
<title></title>
</head>
</html>
In the above example when JavaScript is disabled the browser will redirect to the home page of the web site in 0 seconds. In addition it will also send the parameter javascript=false to the server.
A server side script such as node.js or PHP can then parse the parameter and come to know that JavaScript is disabled. It can then send a special non-JavaScript version of the web site to the client.
This is the "cleanest" solution id use:
<noscript>
<style>
body *{ /*hides all elements inside the body*/
display: none;
}
h1{ /* even if this h1 is inside head tags it will be first hidden, so we have to display it again after all body elements are hidden*/
display: block;
}
</style>
<h1>JavaScript is not enabled, please check your browser settings.</h1>
</noscript>
If javascript is disabled your client-side code won't run anyway, so I assume you mean you want that info available server-side. In that case, noscript is less helpful. Instead, I'd have a hidden input and use javascript to fill in a value. After your next request or postback, if the value is there you know javascript is turned on.
Be careful of things like noscript, where the first request may show javascript disabled, but future requests turn it on.
You might, for instance, use something like document.location = 'java_page.html' to redirect the browser to a new, script-laden page. Failure to redirect implies that JavaScript is unavailable, in which case you can either resort to CGI ro utines or insert appropriate code between the tags. (NOTE: NOSCRIPT is only available in Netscape Navigator 3.0 and up.)
credit
http://www.intranetjournal.com/faqs/jsfaq/how12.html
A technique I've used in the past is to use JavaScript to write a session cookie that simply acts as a flag to say that JavaScript is enabled. Then the server-side code looks for this cookie and if it's not found takes action as appropriate. Of course this technique does rely on cookies being enabled!
I think you could insert an image tag into a noscript tag and look at the stats how many times your site and how often this image has been loaded.
People have already posted examples that are good options for detection, but based on your requirement of "give warning that the site is not able to function properly without the browser having JS enabled". You basically add an element that appears somehow on the page, for example the 'pop-ups' on Stack Overflow when you earn a badge, with an appropriate message, then remove this with some Javascript that runs as soon as the page is loaded (and I mean the DOM, not the whole page).
code inside <noscript> tags will be executed when there is no js enabled in browser.
we can use noscript tags to display msg to turn on JS as below.
<noscript>
<h1 style="text-align: center;">
To view this page properly, please
enable JavaScript and reload the page
</h1>
</noscript>
while keeping our website content inside body as hidden. as below
<body>
<div id="main_body" style="display: none;">
website content.
</div>
</body>
now if JS is turned on you can just make the content inside your main_body visible as below
<script type="text/javascript">
document.getElementById("main_body").style.display="block";
</script>
Why don't you just put a hijacked onClick() event handler that will fire only when JS is enabled, and use this to append a parameter (js=true) to the clicked/selected URL (you could also detect a drop down list and change the value- of add a hidden form field). So now when the server sees this parameter (js=true) it knows that JS is enabled and then do your fancy logic server-side.
The down side to this is that the first time a users comes to your site, bookmark, URL, search engine generated URL- you will need to detect that this is a new user so don't look for the NVP appended into the URL, and the server would have to wait for the next click to determine the user is JS enabled/disabled. Also, another downside is that the URL will end up on the browser URL and if this user then bookmarks this URL it will have the js=true NVP, even if the user does not have JS enabled, though on the next click the server would be wise to knowing whether the user still had JS enabled or not. Sigh.. this is fun...
To force users to enable JavaScripts, I set 'href' attribute of each link to the same document, which notifies user to enable JavaScripts or download Firefox (if they don't know how to enable JavaScripts). I stored actual link url to the 'name' attribute of links and defined a global onclick event that reads 'name' attribute and redirects the page there.
This works well for my user-base, though a bit fascist ;).
You don't detect whether the user has javascript disabled (server side or client). Instead, you assume that javascript is disabled and build your webpage with javascript disabled. This obviates the need for noscript, which you should avoid using anyway because it doesn't work quite right and is unnecessary.
For example, just build your site to say <div id="nojs">This website doesn't work without JS</div>
Then, your script will simply do document.getElementById('nojs').style.display = 'none'; and go about its normal JS business.
Check for cookies using a pure server side solution i have introduced here then check for javascript by dropping a cookie using Jquery.Cookie and then check for cookie this way u check for both cookies and javascript
In some cases, doing it backwards could be sufficient. Add a class using javascript:
// Jquery
$('body').addClass('js-enabled');
/* CSS */
.menu-mobile {display:none;}
body.js-enabled .menu-mobile {display:block;}
This could create maintenance issues on anything complex, but it's a simple fix for some things. Rather than trying to detect when it's not loaded, just style according to when it is loaded.
I would like to add my solution to get reliable statistics on how many real users visit my site with javascript disabled over the total users. The check is done one time only per session with these benefits:
Users visiting 100 pages or just 1 are counted 1 each. This allows to focus on single users, not pages.
Does not break page flow, structure or semantic in anyway
Could logs user agent. This allow to exclude bots from statistics, such as google bot and bing bot which usually have JS disabled! Could also log IP, time etc...
Just one check per session (minimal overload)
My code uses PHP, mysql and jquery with ajax but could be adapted to other languanges:
Create a table in your DB like this one:
CREATE TABLE IF NOT EXISTS `log_JS` (
`logJS_id` int(11) NOT NULL AUTO_INCREMENT,
`data_ins` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
`session_id` varchar(50) NOT NULL,
`JS_ON` tinyint(1) NOT NULL DEFAULT '0',
`agent` varchar(255) DEFAULT NULL,
PRIMARY KEY (`logJS_id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;
Add this to every page after using session_start() or equivalent (jquery required):
<? if (!isset($_SESSION["JSTest"]))
{
mysql_query("INSERT INTO log_JS (session_id, agent) VALUES ('" . mysql_real_escape_string(session_id()) . "', '" . mysql_real_escape_string($_SERVER['HTTP_USER_AGENT']). "')");
$_SESSION["JSTest"] = 1; // One time per session
?>
<script type="text/javascript">
$(document).ready(function() { $.get('JSOK.php'); });
</script>
<?
}
?>
Create the page JSOK.php like this:
<?
include_once("[DB connection file].php");
mysql_query("UPDATE log_JS SET JS_ON = 1 WHERE session_id = '" . mysql_real_escape_string(session_id()) . "'");
I've figured out another approach using css and javascript itself.
This is just to start tinkering with classes and ids.
The CSS snippet:
1. Create a css ID rule, and name it #jsDis.
2. Use the "content" property to generate a text after the BODY element. (You can style this as you wish).
3 Create a 2nd css ID rule and name it #jsEn, and stylize it. (for the sake of simplicity, I gave to my #jsEn rule a different background color.
<style>
#jsDis:after {
content:"Javascript is Disable. Please turn it ON!";
font:bold 11px Verdana;
color:#FF0000;
}
#jsEn {
background-color:#dedede;
}
#jsEn:after {
content:"Javascript is Enable. Well Done!";
font:bold 11px Verdana;
color:#333333;
}
</style>
The JavaScript snippet:
1. Create a function.
2. Grab the BODY ID with getElementById and assign it to a variable.
3. Using the JS function 'setAttribute', change the value of the ID attribute of the BODY element.
<script>
function jsOn() {
var chgID = document.getElementById('jsDis');
chgID.setAttribute('id', 'jsEn');
}
</script>
The HTML part.
1. Name the BODY element attribute with the ID of #jsDis.
2. Add the onLoad event with the function name. (jsOn()).
<body id="jsDis" onLoad="jsOn()">
Because of the BODY tag has been given the ID of #jsDis:
- If Javascript is enable, it will change by himself the attribute of the BODY tag.
- If Javascript is disable, it will show the css 'content:' rule text.
You can play around with a #wrapper container, or with any DIV that use JS.
Hope this helps to get the idea.
Detect it in what? JavaScript? That would be impossible. If you just want it for logging purposes, you could use some sort of tracking scheme, where each page has JavaScript that will make a request for a special resource (probably a very small gif or similar). That way you can just take the difference between unique page requests and requests for your tracking file.