Develop Reference

Is it good to include all js file and css file in the main page as AngularJS way?

I work with AngularJS for several months, but I am still confused at the point: Is it good to include all JavaScript and CSS files in the main page the AngularJS way?
In my opinion, it may cause many conflicts when using many CSS and JS plugins. Also, the web browser loads too many files that may not be used on a specific page. Does this way cause some performance problem?

Does this way cause some performance problem?
AngularJS creed is based on single-page application:
A single-page application (SPA) is a web application or web site that fits on a single web page with the goal of providing a user experience similar to that of a desktop application. In an SPA, either all necessary code – HTML, JavaScript, and CSS – is retrieved with a single page load.
Of course it may cost more in terms of performance at the launch of the application, but it will more fluid/user friendly after.
In my opinion, it may cause many conflicts when i use many css, js
plugins file...
It should not create conflicts. But you have to be carefull when naming your CSS classes, JS files. A convenient way not to override CSS classes is to set prefixes on your classes: CSS classes for view 1 may have a prefix v1-*, classes used throughout the application do not need a prefix. This way you will know which CSS stand for (global or specific for a view). Also think about separate your CSS / JS in different files. Divide and conquer
I would suggest you to use standards (here is a very blog for AngularJS guidelines).

Converting a web app into an embeddable <script> tag

I just did a proof of concept/demo for a web app idea I had but that idea needs to be embedded on pages to work properly.
I'm now done with the development of the demo but now I have to tweak it so it works within a tag on any websites.
The question here is:
How do I achieve this without breaking up the main website's stylesheets and javascript?
It's a node.js/socket.io/angularjs/bootstrap based app for your information.
I basically have a small HTML file, a few css and js files and that's all. Any idea or suggestions?

If all you have is a script tag, and you want to inject UI/HTML/etc. into the host page, that means that an iframe approach may not be what you want (although you could possibly do a hybrid approach). So, there are a number of things that you'd need to do.
For one, I'd suggest you look into the general concept of a bookmarklet. While it's not exactly what you want, it's very similar. The problems of creating a bookmarklet will be very similar:
You'll need to isolate your JavaScript dependencies. For example, you can't load a version of a library that breaks the host page. jQuery for example, can be loaded without it taking over the $ symbol globally. But, not all libraries support that.
Any styles you use would also need to be carefully managed so as to not cause issues on the host page. You can load styles dynamically, but loading something like Bootstrap is likely going to cause problems on most pages that aren't using the exact same version you need.
You'll want your core Javascript file to load quickly and do as much async work as possible as to not affect the overall page load time (unless your functionality is necessary). You'll want to review content like this from Steve Souders.
You could load your UI via a web service or you could construct it locally.
If you don't want to use JSONP style requests, you'll need to investigate enabling CORS.
You could use an iframe and PostMessage to show some UI without needing to do complex wrapping/remapping of the various application dependencies that you have. PostMessage would allow you to send messages to tell the listening iFrame "what to do" at any given point, while the code that is running in the host page could move/manipulate the iframe into position. A number of popular embedded APIs have used this technique over the years. I think DropBox was using it for example.

Organizing Javascript w/ jQuery

I am tinkering around with jQuery and am finding it very useful and almost exciting.
As of now, I am referencing the jQuery script via Google's CDN and I store plugins I use locally in a static/scripts directory.
Naturally, each page has its own individual implementation of components that are required for the features it currently offers. I.E. the main page has the Twitter plugin whereas the login page has form validation logic and password strength metering. However, certain components (navigation bar) for example use the same script across multiple pages.
Admittedly so, I am not a fan of putting javascript code in the header of a page, but I rather prefer to have it in an external file (for caching, re-usability, and optimization purposes).
My question is, what is the preferred route for organizing the external files. I wanted to try and keep it to one javascript file for the entire site to reduce IO requests. However, I am not sure how to implement document ready functions on a conditional per page bases.
$(document).ready(function () { ... }
Is there some way to reference a page by some method (preferably id based and not a url conditional).
Thank you in advance for your time!

You should try REQUIRE JS.
This will allow you to load only those plugins the pages where you need them, and unload them again if they are not needed anymore.
Then again, it might be overkill. It really depends on the size of your project.

Paul Irish:
http://paulirish.com/2009/markup-based-unobtrusive-comprehensive-dom-ready-execution/
This will allow you to block your scripts by body class/ID and execute them automatically.

First you might want to use YUI Compressor or some other JS compressing tool. Then perhaps creating a resource file (resx) for your JavaScript is the way to go. Then just reference the resource within your code. This is the approach Telerik took for their RadControl ASP.NET AJAX control framework.

Javascript and website loading time optimization

I know that best practice for including javascript is having all code in a separate .js file and allowing browsers to cache that file.
But when we begin to use many jquery plugins which have their own .js, and our functions depend on them, wouldn't it be better to load dynamically only the js function and the required .js for the current page?
Wouldn't that be faster, in a page, if I only need one function to load dynamically embedding it in html with the script tag instead of loading the whole js with the js plugins?
In other words, aren't there any cases in which there are better practices than keeping our whole javascript code in a separate .js?

It would seem at first glance that this would be a good idea, but in fact it would actually make matters worse. For example, if one page needs plugins 1, 2 and 3, then a file would be build server side with those plugins in it. Now, the browser goes to another page that needs plugins 2 and 4. This would cause another file to be built, this new file would be different from the first one, but it would also contain the code for plugin 2 so the same code ends up getting downloaded twice, bypassing the version that the browser already has.
You are best off leaving the caching to the browser, rather than trying to second-guess it. However, there are options to improve things.
Top of the list is using a CDN. If the plugins you are using are fairly popular ones, then the chances are that they are being hosted with a CDN. If you link to the CDN-hosted plugins, then any visitors who are hitting your site for the first time and who have also happened to have hit another site that's also using the same plugins from the same CDN, the plugins will already be cached.
There are, of course, other things you can to to speed your javascript up. Best practice includes placing all your script include tags as close to the bottom of the document as possible, so as to not hold up page rendering. You should also look into lazy initialization. This involves, for any stuff that needs significant setup to work, attaching a minimalist event handler that when triggered removes itself and sets up the real event handler.

One problem with having separate js files is that will cause more HTTP requests.
Yahoo have a good best practices guide on speeding up your site: http://developer.yahoo.com/performance/rules.html
I believe Google's closure library has something for combining javascript files and dependencies, but I havn't looked to much into it yet. So don't quote me on it: http://code.google.com/closure/library/docs/calcdeps.html
Also there is a tool called jingo http://code.google.com/p/jingo/ but again, I havn't used it yet.

I keep separate files for each plug-in and page during development, but during production I merge-and-minify all my JavaScript files into a single JS file loaded uniformly throughout the site. My main layout file in my web framework (Sinatra) uses the deployment mode to automatically either generate script tags for all JS files (in order, based on a manifest file) or perform the minification and include a single querystring-timestamped script inclusion.
Every page is given a body tag with a unique id, e.g. <body id="contact">.
For those scripts that need to be specific to a particular page, I either modify the selectors to be prefixed by the body:
$('body#contact form#contact').submit(...);
or (more typically) I have the onload handlers for that page bail early:
jQuery(function($){
if (!$('body#contact').length) return;
// Do things specific to the contact page here.
});
Yes, including code (or even a plug-in) that may only be needed by one page of the site is inefficient if the user never visits that page. On the other hand, after the initial load the entire site's JS is ready to roll from the cache.

The network latency is the main problem.You can get a very responsive page if you reduce the http calls to one.
It means all the JS, CSS are bundled into the HTML page.And if your can forget IE6/7 you can put the images as data:image/png;base64
When we release a new version of our web app, a shell script minify and bundle everything into a single html page.
Then there is a second call for the data, and we render all the HTML client-side using a JS template library: PURE
Ensure the page is cached and gzipped. There is probably a limit in size to consider.We try to stay under 400kb unzipped, and load secondary resources later when needed.

You can also try a service like http://www.blaze.io. It automatically peforms most front end optimization tactics and also couples in a CDN.
There currently in private beta but its worth submitting your website to.

I would recommend you join common bits of functionality into individual javascript module files and load them only in the pages they are being used using RequireJS / head.js or a similar dependency management tool.
An example where you are using lighbox popups, contact forms, tracking, and image sliders in different parts of the website would be to separate these into 4 modules and load them only where needed. That way you optimize caching and make sure your site has no unnecessary flab.
As a general rule its always best to have less files than more, its also important to work on the timing of each JS file, as some are needed BEFORE the page completes loading and some AFTER (ie, when user clicks something)
See a lot more tips in the article: 25 Techniques for Javascript Performance Optimization.
Including a section on managing Javascript file dependencies.
Cheers, hope this is useful.

Integrate Javascript resources in HTML: what's the best way?

I'm working on a project which uses many scripts (Google Maps, jQuery, jQuery plugins, jQuery UI...). Some pages have almost 350 kB of Javascript.
We are concerned about performance and I'm asking myself what is the best way to integrate those heavy scripts.
We have 2 solutions:
Include all scripts in the head, even if they are not utilized on the page.
Include some common scripts in the head, and include page specific ones when they are needed.
I would like to have your advice.
Thanks.

For the best performance I would create a single static minified javascript file (using a tool like YUI compressor) and reference it from the head section. For good tips on website performance check out googles website optimizations page.
Note that the performance penalty of retrieving all your javascript files only happen on the first page, as the browser will use the cache version of the file on subsequent pages.
For even better responsiveness you would split your javascript in two files. Load the first with all the javascript you need when the page loads, then after the page loads load the second file in the background.
If your interested, I have an open source AJAX javascript framework that simplifies compresses and concatenates all your html, css and javascript (including 3rd party libraries) into a single javascript file.

If you think it's likely that some users will never need the Google Maps JavaScript for example, just include that in the relevant pages. Otherwise, put them all in the head - they'll be cached soon enough (and those from Google's CDN may be cached already).

Scripts in the <head> tag do (I think) stop the page from rendering further until they’ve finished downloading, so you might want to move them down to the end of the <body> tag.
It won’t actually make anything load faster, but it should make your page content appear more quickly in some situations, so it should feel faster.
I’d also query whether you’ve really got 350 KB of JavaScript coming down the pipe. Surely the libraries are gzipped? jQuery 1.4 is 19 KB when minifed and gzipped.

1) I would recommend gather all the common scripts and most important like jquery and etc in one file to reduce number of requests for this files and compress it and i would recommend google closure u will find it here
2) Make the loading in a page the user have to open it in the beginning like login page and put the scripts at the end of the page to let all the content render first and this recommended by most of the performance tools like yslow and page speed
3) don't write scripts in your page , try to write everything in a file to make it easier later on for compression and encryption
4) put the scripts and all statics files like images and css on other domain to separate the loading on your server