I am trying to understand JavaScript minification and compression processes and have couple of questions on these:
Since minification makes the code difficult to debug, is it possible to do on-demand de-minification on client-side to cover-up for cases where you actually need to debug and investigate something on the website?
I remember reading somewhere that one can enable compression of all resources (like images, CSS, JavaScript etc.) by setting some options in the Apache Web Server. Is there any difference in the JavaScript compression done at Apache level and, the one done using tools like YUI Compressor?
Can someone help me know the above?
The kind-of cases where I would actually need to de-minify my JavaScript files is let's say a JavaScript error happened at line no. X. With a minified files it would be very tough to know which block of code caused that error in production as the lines are all wrapped up in a minified file. How do you guys investigate and debug in such circumstances? Another user also mentioned this debugging problem in Packed/minified javascript failing in IE6 - how to debug? questions (slightly specific to IE6 though).
You shouldn't be debugging minified code. Ideally, development process is like this:
You build and debug the site locally. You have full versions of javascripts, stylesheets and everything.
You deploy a version to production machine. You minify and gzip a copy of your assets and push that to the server. Your local development copy is left untouched.
If there's a bug in production, you modify your local version, minify, compress, upload.
Repeat until PROFIT
Chrome Dev Tools can de-obfuscate (and de-minify) javascript code if you want to debug production code (useful when trying to replicate a bug on a live environment you may not be seeing in dev)
Typically developers will develop against the uncompressed script file, compress right before deploying.
If you have to go back and debug your script files, you'd just open up the regular, uncompressed file, do your work, compress, and deploy. If you mean debug something while your website is in production, then no, you can't un-minify your script file on demand.
And yes, Apache, and even IIS, can gzip compress scripts and images automatically for you.
Since minification makes the code difficult to debug, is it possible
to do on-demand de-minification on client-side to cover-up for cases
where you actually need to debug and investigate something on the
website?
Sort of. Minified javascript has the same structure, it just does things like delete extra spaces and shorten variable names. So you can easily make the code readable again, either manually or with a script, but you can't recover variable names, so the code will still be harder to work with. So, if you have the original code, definitely don't get rid of it. Save the minified code separately.
I remember reading somewhere that one can enable compression of all
resources (like images, css, javascript etc.) by setting some options
in the Apache Web Server.
Yes, it's called gzip compression. It's not unique to apache, but you would need to configure your server to enable it.
Is there any difference in the javascript compression done at Apache
level and, the one done using tools like YUI Compressor?
Yes. YUI compressor is a minifier - the output is valid javascript. Server-side compression is more analogous to zipping a file - the browser must decode it before it can be used. Using the two together would yield the smallest filesize.
I prefer working with a local unminified copy of the JS-file, and when i deploy the site, I minify all JS-files into one. That way it is easy to debug and improve the code. However, there are tools to revert minification. Have a look at this SO post on revert minification of JavaScript.
Have a look at GZIP compression - This blog describe how to enable GZIP in Apache and how to verify that your server actually is compressing the files.
is it possible to do on-demand de-minification on client-side
Some browsers have a "pretty code" view that automatically formats source code. See Firebug's CSS tab.
Is there any difference in the javascript compression done at Apache level and, the one done using tools like YUI Compressor?
YIU Compressor is a actually a minifier. Apache compression is like ZIP-ing up the file before it is sent to the client so the actual file that is sent is smaller than the file on disk. They are two different technologies that are independent of each other.
Related
I compress all my JavaScript files and CSS files with YUI Compressor
yuicompressor -o '.js$:.min.js' *.js -v
Should I keep the minified files in my subversion system or not?
I know both is possible but I'm searching for "best practice" and the pros and cons
My opinion is that it is a better to have that as part of the building process.
And builds should not be in the version tracking system for the source code.
For that reason, minified javascript files shouldn't be there either.
I think it would be best to leave out any minified files.
The reason for this is, if you have a junior come in to work on your site and they see the minified files, but not the other files, they might end up formatting your minified file so it's more readable, make changes and then when you go back to edit the correct file and compress, all his work has gone.
Worst case scenario when you don't include them is the junior will ask why his changes haven't displayed on the site and you can explain to him the correct tools which you are currently using.
OKay, this answer will purely depend on your project. Say if your project engine is capable of producing minified files, then you may not need to do this.
But say, if this is the same exact code that has to be deployed in your webserver, and all your HTML files depend on the minified code, then you have to add this.
In a nutshell, in doubt, keep the file!
SVN (or got or any versioning system) is there for keeping track of the code, not of the releases thus (IMO) it does not make sense to keep a version of the releases.
It is better to let a dedicated tool handling that (like artifactory)
Minified versions should not be in source system if you are able to generate them from the actual files in a controlled manner. This would imply that you have a build system and tools in place that is also controlled. For e.g. let's say that someone changes your YUI compressor version tomorrow. If you don't have the old version somewhere your build could break.
With the same logic, it would make sense to keep both the minified and unminified versions of any 3rd party libraries.
We have a website say 'abc.com' which uses lot of javascript and css hosted on another server 'xyz.com'. We upload js and css on to this server and it gives us a URL, which we use/reference in our code.
Now I ran YSLOW on my website, and it complains that these javascript and css files can be compressed. When I inspect response headers using firebug, Content Encoding of response is set to 'GZip'.
My question would be 'how to enable compression for these javascript and css files, hosted on other server'. Is there something, we can do on our side?
Any suggestions are welcome.
You will have to use tools like YUI compressor to compress your js and css files, before uploading to the server.
EDIT:
Please check this link on how to enable gzipping your js and css files. But, I doubt it is possible for you to do this since the files are hosted on third server(unless you are managing it).
JavaScript and CSS compression goes beyond typical all-purpose compression algorithms like gzip.
There are domain specific solution for compressing JavaScript and CSS.
See:
http://developer.yahoo.com/yui/compressor/
http://code.google.com/closure/compiler/
https://github.com/mishoo/UglifyJS
To clarify the terminology used by YSlow (and similar tools like Google's PageSpeed):
Compression reduces response times by reducing the size of the HTTP response. Gzip is the most popular and effective compression method currently available and generally reduces the response size by about 70%. Approximately 90% of today's Internet traffic travels through browsers that claim to support gzip.
Minification removes unnecessary characters from a file to reduce its size, thereby improving load times. When a file is minified, comments and unneeded white space characters (space, newline, and tab) are removed. This improves response time since the size of the download files is reduced.
Some good references that cover both compression and minification:
Yahoo: http://developer.yahoo.com/performance/rules.html
Google: http://code.google.com/speed/page-speed/docs/payload.html
Stoyan Stefanov: http://www.phpied.com/reducing-tpayload/ (examples for Apache+PHP, but can apply to any web server)
As robert mentioned in his answer, enabling compression on the other server would be a configuration change on that side. If you wanted to minify the JS/CSS components, you could do that with a minification tool prior to hosting on the other server.
As far i know until now, the min version of a .js(javascript) file is obtaining by removing the unncessary blank spaces and comments, in order to reduce the file size.
My questions are:
How can I convert a min.js file into a clear, easy readable .js file
Besides, size(&and speed) are there any other advtages of the min.js file.
the js files can be encripted?
can js be infected. I think the answer is yes, so the question is how to protect the .js files from infections?
Only the first question is most important and I'm looking for help on it.
TY
To convert a minified file into a editable source, simply open any IDE that supports auto-formatting and auto-format it. I use Netbeans to do this.
If you do client side caching for the minified file, it means to say that the client (computer) needs to process less bytes. Size and speed are the main advantages of a minified file, and they are already great advantages to prepare for a future that requires great load of data transfer. By the way, it also saves you some bandwidth on your server and therefore money.
I don't see the need of encryption. See How to disable or encrypt "View Source" for my site
Javascript files cannot be edited unless it is done so on the server. The security of your Javascript files depends on your 1) server protection 2) data protection. Data should not be able to exploit. But of course, Javascript is executed on the client side, it will be meaningless for the client user to attack him/herself. However Twitter has shown multiple Javascript exploits. You need to constantly test and check your codes against XSS, CSRF and other attacks. This means to say that if your Javascript file has a loophole, it was the developer, you, who created it.
Multiple minifiers exists, that also are able to compress JS, see http://dean.edwards.name/weblog/2007/04/packer3 for one of the most being used. Some others exists, also see the JSMin library http://www.crockford.com/javascript/jsmin.html
The main advantage is the size gain. You should also aggregate your JS files when you have multiple JS files, this also saves a lot of I/O (less HTTP requests) between the server and the client. This is probably more important than minifying.
I can't answer you about encryption. Client security will mainly depend on its browser.
EDIT: Ok my first answer is not for the first question, merged both in 2.
Is there any software package/library that will produce a consolidated, minified JavaScript file for a production environment, while leaving the original files/references as-is in a development environment (so developers can work independently)?
JAWR does this (and more) for a Java/Groovy environment, but I haven't seen anything like it for the Microsoft .NET/IIS7 stack. Any pointers would be helpful. Thanks!
If you're looking for a good way to automatically compress and combine css & js files here are some options:
Xpedite Not bad: has one big disadantage: you can't combine files (js/css) that are included in usercontrols with the files in your page.
Shinkansen, I don't have a lot of experience with it, but I know it has a lot of configuration options.
The ClientDependency Framework was originally written for Umbraco. Now there is a package available via NuGet for both WebForms and MVC. It works really well and this is my favorite.
We use YUICompressor to minify our Javascript (and CSS) and it works well.
However, we've had to write our own HttpHandler to decide whether to minify or not on the fly, depending on a config setting (but it could equally be on whether it was a DEBUG or RELEASE build).
In fact, we cache the file once minified (or not), so we don't have to do the same process on every request.
I've been using yuicompressor.jar on my test server for on-the-fly minimisation of changed JavaScript files. Now that I have deployed the website to the public server, I noticed that the server's policies forbid the use of exec() or its equivalents, so no more java execution for me.
Is there a decent on-the-fly JS compressor implemented in PHP? The only thing resembling this that I was able to find was Minify, but it's more of a full-blown compression solution with cache and everything. I want to keep the files separate and have the minimised files follow my own naming conventions, so Minify is a bit too complex for this purpose.
The tool, like yuicompressor, should be able to take either a filename or JavaScript as input and should either write to a file or output the compressed JavaScript.
EDIT: To clarify, I'm looking for something that does not have to be used as a standalone (i.e. it can be called from a function, rather than sniffing my GET variables). If I just wanted a compressor, Minify would obviously be a good choice.
EDIT2: A lot has changed in the five years since I asked this question. Today I would strongly recommend separating the front-end workflow from the server code. There are plenty of good tools for JS development around and except for the most trivial jQuery enhancements it's a better idea to have a full workflow with automated bundling, testing and linting in place and just deploy the minified bundles rather than the raw files.
Yes there is, it's called minify.
The only thing in to worry about in the way of complexity is setting up a group, and there's really nothing to it. Edit the groupsConfig.php file if you want multiple JS/CSS in one <script> or <link> statement:
return array(
'js-common' => array('//js/jquery/jquery-1.3.2.min.js', '//js/common.js', '//js/visuals.js',
'//js/jquery/facebox.js'),
'css-common' => array('//css/main.css', '//css/layout.css','//css/facebox.css')
);
To include the above 'js-common' group, do this:
<script type="text/javascript" src="/min/g=js-common"></script>
(i know i was looking for the exact same thing not knowing how to deal directly with the jar file using php - that's how i ended up here so i'm sharing what i found)
Minify is a huge library with tons of functionalities. However the minifying part is a very tiny class : http://code.google.com/p/minify/source/browse/trunk/min/lib/Minify/YUICompressor.php
& very very easy to use :
//set the path to the jar file
Minify_YUIcompressor::$jarFile=_ROOT.'libs/java/yuicompressor.jar';
//set the path to a writable temp folder
Minify_YUIcompressor::$tempDir=_ROOT.'temp/';
//minify
$yourcssminified=Minify_YUIcompressor::minifyCss($yourcssstringnotminified,$youroptions)
same process for js, if you need more functionalities just pick from the library & read the source to see how you can make direct call from your app.
I didn't read the question well, since minify is based on using the jar files, the op can't use it anyway with his server config
Minify also include other minifying methods than yui, for example:
http://code.google.com/p/minify/source/browse/trunk/min/lib/JSMinPlus.php?r=443&spec=svn468
Try Lissa:
Lissa is a generic CSS and JavaScript loading utility. Lissa is an extension of the YUI PHP Loader aimed at solving one of the current loader limitations; combo loading. YUI PHP Loader ships with a combo loader that is capable of reducing HTTP requests and increasing performance by outputting all the YUI JavaScript and/or CSS requirements as a single request per resource type. Meaning even if you needed 8 YUI components which ultimately boil down to say 13 files you would still only make 2 HTTP requests; one for the CSS and another for the JavaScript. That's great, but what about custom non-YUI resources. YUI PHP Loader will load them, but it loads them as separate includes and thus they miss out on benefits of the combo service and the number of HTTP requests for the page increases. Lissa works around this limitation by using the YUI PHP Loader to handle the loading and sort of YUI and/or custom resource dependencies and pairs that functional with Minify.