Best way to use JavaScript in a HTML page - javascript

What is the best way to import and use JavaScript code in HTML pages? I am considering two options:
Have single <script> tag with all.js file that is imported to HTML files, that uses selected JavaScript methods.
Define separate <script> tag in each HTML file separately.
What is the best design option here?

Lukasz, this innocent question is a big topic. To get started with JavaScript performance and maintainability in a nice place, follow Steve Souders' writings on this.
And use JSHint. That's much easier if your code is in a JavaScript-only file. To find out about other good practices, read idiomatic.js.

A single minified file is the most performant - less requests and smaller download. But not one global js for everywhere, that would be a pain to debug/develop.
Use a cdn for libraries as probably cached in browser.

IMO I will have separate tags for separate javascript snippets/plugins, it will make my javascript code easier to maintain. I can remove the plugin/add the plugin without disturbing the other javascript snippets.
But for performance issue, modern browsers will run 6 consecutive threads to download the resources, so it will be good idea to profile the loading times of the site/web app. You can use tools like Firebug/yslow to profile http requests being sent from the html page.
Personally I use template engines like Sitemesh and create templates for jsps for different parts of the application.
And for javascript I mainly use JQuery and a lot of plugins.

Minify js is a good and acceptable way. it also helps to build js files on the server side at run time. This is a big topic. Here are some good advices from yahoo. I use these as my guidlines. Also read on the topic js minify
http://developer.yahoo.com/performance/rules.html

Related

Combining and Compressing multiple JavaScript files into a single file in a Django project

What is the simplest way to combine JavaScript files into a single file in a Django project?
Explanation
I want this to work with Ember.js/Backbone where you (usually) have many different JavaScript in multiple directories. Directories would all be in one folder called app/ for example, like: app/views/ app/models/ /app/routers/
Requirements
Work together with the staticfiles app
Still be separated while in development mode for easier debugging (only compile when calling collectstatic?)
Work with Require.js (guess that shouldn't be too hard, but putting it in here to be sure)
Extra credit
Explain a best practices way of combining Django and Ember/Backbone.
I am an happy user of django compressor, it does combine, minify, debug-friendly, you can use it with staticfiles, easy to plug with custom storage backend (eg. S3)
https://github.com/jezdez/django_compressor
The reason you want to combine many files into one is so to minimize latency of setting up and tearing down http requests, the fewer you make the better. However, many newer browsers are downloading JavaScript files in parallel (still executing sequentially). The consequence is that downloading a single 1Mb file may be slower than three 350Kb files.
you can use from CDNs.
As mentioned in the previous answer, django-compressor is nice, but you often get better loading times when using a dedicated javascript loader instead. My tip is to check out Head.js for example (http://headjs.com/) (there are tons other out there as well). Often combining scripts can be contra productive when considering caching, using javascript located on CDN:s etc.
One thing to remember is that Iphone 3/4 will just cache 15/25KB of javascript, so if you have huge scripts and combine them you can run into trouble. http://www.phpied.com/iphone-caching/

Break up JavaScript file into more manageable, or using different IDE

I use Dreamweaver for development, mostly PHP, html, css, javascript. Is there anyway to break up JavaScript files? or maybe a better IDE that makes it easier to work with? It just becomes quickly difficult to read and find what I'm looking for.
Thank you!
Intellij and/or Webstorm by Jetbrains has the best JS tools I have found. It has very good (as good as it gets, for JS) intellisense (autocomplete for variables and methods) as well as refactoring for variables and methods. You can cmd+click into method definitions from anywhere, as well. Unfortunately you need to pay for them, but if you are using Dreamweaver you had to pay for that. If you are only doing html/css/javascript Webstorm is the way to go.
Yes, you should break up your javascript files into relevant parts just like you break up your php files into relevant parts. The one key factor here is they should be combined and minified before being served up to the browser so the user does not have to make several network calls to your server for each .js file.
Check out Google Minify for an easy solution to that issue.
Take a look at the JQuery source to see how they divvy up their files. Now look at their combined framework, and of course their minified framework. What is actually served up to the user looks nothing like the source.
Uh, Dreamweaver?
Definitely use a different IDE. Aptana won the poll here :)

How should I start a new JavaScript project (Testing, Developing, Building)?

I've developing JavaScript since many years but have never really thought about the whole testing, developing and building stuff - but I realized it's pretty much necessary. We've just used a Subversion repository with simple release tagging (switching to git soon). As a new bigger pure JavaScript project (using jQuery) is arriving soon, I'd like to optimize the whole process.
I already did some research but never found a good starting tutorial.
It's definetly a good idea to split classes and separate code blocks into several js-files and not a big one (as Prototype or jQuery do it). These js-files must be "build" into a single file. How do I achieve that?
It's pretty much necessary to Unit-test the stuff me and my colleagues are coding. I found the js-test-driver which has an eclipse plugin that seems to be doing his job quite good. If my developer-folder contains all these src- and src-test-files, how do I integrate this in the building process?
For testing, take a look at this: https://stackoverflow.com/questions/32809/javascript-unit-testing
For merging all of your JavaScript into one file you can use something like YUI Compressor. You need to be looking for a minimizer first, compression second. A minimizer just takes the files and merges them together and gets rid of whitespace. A compressor will actually try to optimize the js for you by changing variable names and removing unnecessary code.
As for unit testing I am unsure of how you will want to do that. There are a few unit test libraries out there. A popular tool for testing is Selenium. I don't currently do unit testing so I am out of my element there..
For setting up your code you could always look at using a JavaScript framework like ExtJS or JavaScriptMVC. Those help you with setting up your code in the proper way and also helps focus your team on the proper standards and coding structure while also writing a lot of the code for you so you don't have to re-invent the wheel.
EDIT: Just a quick after thought. Even if you don't want to use a JavaScript framework, I would suggest checking them out, especially ExtJS, just to see how they organize their code and some of the tricks they do to keep it clean.
I'll answer part of your question:
These js-files must be "build" into a
single file.
This is possible only with server side language - in ASP.NET you have built in tools for that, otherwise build your own "merger" server side file and reference that file instead of the actual .js files.
These js-files must be "build" into a single file. How do I achieve that?
Definitely keep your files separate in version control, and only merge them during the build process.
The YUI compressor mentioned elsewhere is a java-based tool that will not only merge but -- of course! -- compress your files for faster download.
If you just want a simple merge of files, a simple Perl or bash-script (or other preferred scripting language) could concatenate multiple .js files into one for release -- just make sure that the build script also updates all HTML in the release to reference only the single page.

How to update HTML script and link references when combining JavaScript and CSS files?

Multiple sites reference combining JavaScript and CSS files to improve web page performance, including examples of using ANT build scripts to concatenate the files prior to deployment.
I've search, and haven't found any information how to automate updating references to those files in HTML and other documents. I am looking to avoid hacking together something error prone, and want to learn from others who have automated builds in the past.
Are there automated tools in the wild to complete this task that I'm not seeing? Are there recommended processes to update the script and link tags in HTML? Can these solutions be integrated with ANT or similar build tools?
There sure is and it's a smart thing to do.
I found a PHP solution, don't know it that's okay for you, but if it isn't you can still read it's source (it's not difficult) and learn a lot. The solution works like this:
Rewrite your requests like this: from css/main.css and css/skin.css to css/main.css,skin.css (of course you can put many more).
Use apache's mod_rewrite to redirect this request to a script (in our case combine.php), that will combine all files to a single one.
The script combines all the files and sends the combined file. Then it saves it to a cache folder.
Next time around it checks if there is an up-to-date version of the cache and serves that one. If the latest file modification time has changed, it discards the cache.
The solution works great and it even makes use of HTTP cache headers and spits out an [ETags], which you should do anyway.
You are correct this is a great way to speed up page loading. It will even work in conjunction with a CDN, which the other poster recommended.
Here is a small script that will pack multiple files in to one for deployment. It supports both JS and CSS, and will even "minify" them by removing whitespace, etc. Just hook this in to your build and deploy scripts.
juicer: http://cjohansen.no/en/ruby/juicer_a_css_and_javascript_packaging_tool
What even better, it will follow JS and CSS import statements, so you only need to point your HTML files to the loader file and it will work in both development and production. (Assuming you replace the loader file with the combined file on deployment.)
There are others, including some run-time solutions. But it sounds like you have a build process in place anyway.
As far as HTML updating, if you still need it, since automated deployments are very popular in the Ruby world, and you may find some standalone utilities to help even for non-ruby projects. (As above) Methinks this would be best handled by your own project's template language, though. (With a static resource revision id, or such.)
Good luck, and let us know what you find.
I think what you really want is a CDN Content Delivery Network.
Read about it here
http://developer.yahoo.com/performance/rules.html
http://en.wikipedia.org/wiki/Content_delivery_network

YUICompressor or similar in PHP?

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.

Categories