So, I'm new to dynamic web design (my sites have been mostly static with some PHP), and I'm trying to learn the latest technologies in web development (which seems to be AJAX), and I was wondering, if you're transferring a lot of data, is it better to construct the page on the server and "push" it to the user, or is it better to "pull" the data needed and create the HTML around it on the clientside using JavaScript?
More specifically, I'm using CodeIgniter as my PHP framework, and jQuery for JavaScript, and if I wanted to display a table of data to the user (dynamically), would it be better to format the HTML using CodeIgniter (create the tables, add CSS classes to elements, etc..), or would it be better to just serve the raw data using JSON and then build it into a table with jQuery? My intuition says to do it clientside, as it would save bandwidth and the page would probably load quicker with the new JavaScript optimizations all these browsers have now, however, then the site would break for someone not using JavaScript...
Thanks for the help
Congratulations for moving to dynamic sites! I would say the following conditions have to be met for you to do client-side layout (it goes without saying that you should always be doing things like filtering DB queries and controlling access rights server side):
Client browser and connection capabilities are up to snuff for the vast majority of use cases
SEO and mobile/legacy browser degradation are not a big concern (much easier when you synthesize HTML server side)
Even then, doing client-side layout makes testing a lot harder. It also produces rather troublesome synchronization issues. With an AJAX site that loads partials, if part of the page screws up, you might never know, but with regular server-side composition, the entire page is reloaded on every request. It also adds additional challenges to error/timeout handling, session/cookie handling, caching, and navigation (browser back/forward).
Finally, it's a bit harder to produce perma-URLs in case someone wants to share a link with their friends or bookmark a link for themselves. I go over a workaround in my blog post here, or you can have a prominent "permalink" button that displays a dynamically rendered permalink.
Overall, especially when starting out, I would say go with the more kosher, better supported, more tutorialed, traditional approach of putting together the HTML server side. Then dip in some AJAX here and there (maybe start out with form validation or auto-completion), and then move on up.
Good luck!
It is much better to do the heavy lifting on the server side.
In CodeIgniter you create a view, looping through all the rows in the table adding in the classes or whatever else you would need. There is no reason at all to do this in Javascript.
Javascript is a sickly abused language with unfortunate syntax. Why on earth would you want to load a page, and then issue a AJAX call to load up some JSON objects to push into a table is beyond me. There is little reason to do that.
Javascript (and jQuery) is for end user enhancement. Make things slide, flash, disappear! It is not for data processing in even the mildest of loads. The end user experience would be crap because you're relying on their machine to process all the data when you have a server that is infinitely more capable and even designed for this specifically.
It depends on your target market and the goal of your site.
I strongly believe in using the client side where ever you can to offload work from the server. Obviously its important you do it correctly so it remains fast for the end user.
On sites where no-js support is important (public websites, etc), you can have fallbacks to the server. You end up doubling code in these situations but the gains are very beneficial.
For advanced web applications, you can decided if making JS a requirement is worth the trade of losing a (very) few users. For me, if I have some control over the target market, I make it a requirement and move on. It almost never makes sense to spend a ton of time to support a small percentage of potential audience. (Unless the time is spent on accessibility which is different, and VERY important regardless of how many people fit into this group on your site.)
The important thing to remember, is touch the DOM as little as possible to get the job done. This often means building up an HTML string and using a single append action to add it to the page vs looping through a large table and adding one row at a time.
It's better to do as much as possible on the server-side because 1) you don't know if the client will even have JavaScript enabled and 2) you don't know how fast the client-side processing will be. If they have a slow computer and you make them process the entire site, they're going to get pretty ticked off. JavaScript/jQuery is only supposed to be used to enhance your site, not process it.
You got the trade-off correctly. However, keep in mind that you can activate compression in the server side, which will probably make adding repetitive markup to format the table a small bandwidth cost.
Keep also in mind that writing Javascript that works in all browsers (including hand-helds) is more complicated than doing the same server side in PHP. And don't forget that the "new JavaScript optimizations" do not apply to the same extent to browsers of handheld devices.
I do a great deal of AJAX app development and I can tell you this from my experience. a good balance between the two is key.
do the raw data server-side but use javascript to make any modifications that you would need to it. such as paging, column sorting, row striping, etc.
I absolutely love doing everything in AJAX heh.. but there are some short falls to doing it using AJAX, and that's SEO. search engines do not read javascript, so for the sake of your website's page rank, I would say have all data served up server side and then formatted and made look cool client-side.
The reason I love AJAX so much is because it drastically speeds up your APP usage by the user as it only loads the data you need to load where you need to load it, versus load the entire page every time you do something... you can do a whole bunch of stuff, such as hide/show rows/columns (we are talking about table manipulation here because you mentioned a table) and even with these show/hide actions add delete actions where when you click a delete row or button it deletes that row not only visually but in the database all done via AJAX calls to server-side code.
in short.
raw data: server-side sending to the client the raw data in html layout (tables for table structured data, however I do everything else in divs and other flexible html tags, only do tables for column/row style data)
data formatting: client-side which also includes any means of interacting with the data. adding to it, deleting from it, sorting it differently etc. This achieves two things. SEO, and User Experience (UX).
Related
Should I have my server return JSON data and then have the JavaScript parse it to create / render HTML directly or should I have my server-side code return HTML directly, which can be directly placed by the JavaScript.
Thoughts?
Render the code server side (e.g. as it is done in Rails' AJAX), then return the view to the client where it will just be placed.
Then profile your code. If it turns out to be too slow, return the JSON and think of a way to render it client-side.
Your priority for this should be to not make the whole thing too copmlicated.
I'm not a fan of returning generated HTML. IMHO I'd return JSON and use something like JQOTE 2 to handle the rendering. Let the clients resources handle that work.
(Side note: JQOTE is an amazing tool!)
I think that if you won't need the data later, e.g. for filtration, on-the-fly search, etc, then you should return HTML.
Premature optimization is the root of all evil. Start with whatever is easier. If it's just too slow, find a way to optimize (perhaps by using an alternative).
If one is not easier than the other to you, go with the server side. I can't imagine a circumstance where a server side scripting language operation would be slower than javascript in a browser.
If all you have to do is render HTML, then it's probably much easier to do it directly with the server (php). Otherwise, you have to convert it to JSON with php first, then convert it back with JS later. That's at least one extra step and extra work for the javascript side.
I'll vote for your first proposed approach.
JSON serialized data size is smaller than (X)HTML one and your first approach saves a lot of CPU cicles, network traffic, memory and speeds-up your client, which ends in a responsive user interface.
Just send data in JSON format and parse it in JavaScript in the client-side so things will be more simpler in the server and rendering things will be delegated to client web browser.
There is no one right answer; it depends on your expectations.
If you want the application to be accessible (ie. processed by a screen reader), picked up by search engine bots or want the UI to be cacheable between requests and users, you will have to use server generated HTML and no dynamic loading. If you use a cache for the generated HTML, you get a lot of mileage without the constant re-rendering. There are more server side tools than client side but that is becoming less of a true statement as JS grows.
OTOH, producing JSON that is rendered by the client using some JS library can really help your server reduce load. You're distributing the work of rendering to the client but that does take control out of your hands. If you have a JS heavy solution and the client can't process JS (screen readers, search engine bots, etc), then the site should degrade gracefully or expect to have some audience that can't view it. That audience might be minuscule for you but it's something to know. As long as you manage the rendering well, (set min size for areas, wait icons, etc) then you can have client side rendering that is as smooth as server side (when comparing visual rendering steps). Producing JSOn also gives you more flexibility as more interfaces are defined or other non-UI clients become important.
It depends on what you are trying to achieve. If you are writing a mobile application you may want to save bandwidth and work with client-side templates (just as an example: John Resig's micro templates). If bandwith is not that important to you I would just use server-side templates to generate the HTML you need.
In my opinion it's all about responsiveness. Your server is ALWAYS going to be able to process data faster than the UA, however the difference between the two may be negligible. If that's the case, then I'd recommend passing JSON to the UA and then use client-side code to do the dirty work. That way, you'll have clear separation of concerns between the server and the client, allowing you to deliver JSON data to different client endpoints in the future without having to modify your server-side code.
However, if there is a significant performance hit with doing the data processing on the client side then it might make more sense to deliver HTML directly to the client. HOWEVER I highly recommend that you still deliver JSON, only to your server-side HTML creation function (rather than the UA) so that you can still deliver JSON data to multiple endpoints without having to alter core code in the future.
I know this seems like a really subjective question, but from what I'm reading, I'm generally confused. We are developing a web-based application that has tabbed windows, etc-very much a "desktop-like" application graphically. About half the page never or rarely changes, and the other half is content that could be handled dynamically within a main window.
So from the ajax proponents, this seems like a perfect example of something that would benefit from ajax. The only thing stopping me (other than lack of ability :-D) is that I'm concerned we would degrade the speed of the app (which isn't really all that great anyway...)
Can anyone either shed some light on this subject or point me to more reading material on performance differences when changing lots of data at once via ajax?
About the differences that can often be seen :
If you load more data via AJax requests, and less via "full-page" requests, it means :
less data will go through the network (only content of pages, not menus, sidebars, ...)
less thins to generate on the PHP/SQL side (same : no menu, ...)
But more Ajax requests can also mean more requests, depending on how your application is developped
Which can mean more load on the server...
You also might want to think about :
Indexation by search engines,
Accessibility,
Graceful degration,
and all the possible stuff like that...
Which, in the end, can mean you'll maybe spend lots of additionnal time developping the "more Ajax" version ; and time is money -- and a few days of developper-time can cost more than renting/buying a second server.
In the end, I would say what really matter is not "performance" : you'll probably have greater gains spending a couple of days optimizing what you already have (profiling on the backend side, minifying/compressing JS/CSS, merging JS/CSS files to have less HTTP requests, ...) than by transforming everything to "full-Ajax".
And, of course, what really matters is user-experience !
As someone who just finished developing a similiar application i can say that using ajax to create a "desktop - like" application.... well... looks cool....
But there are certain points that you should be considering before you start...
Dealing with forms when you a load a page with ajax will require the additional knowledge of a javascript framework like Jquery.... Because loading a page portion of a page with ajax does not affect the DOM tree of the page and hence the newly added elements will not be identified by javascript functions.... That's where you will be needing the livequery plugin for jquery.
If you are looking do develop a site optimized for search engine indexing.... ajax - refreshed content may not be a good idea. I developed only the backend part. i.e the administrator module like a desktop application. The frontend where the user actually interact was your normal, day-to-day, website...!!
When is it appropriate to use AJAX?
what are the pros and cons of using AJAX?
In response to my last question: some people seemed very adamant that I should only use AJAX if the situation was appropriate:
Should I add AJAX logic to my PHP classes/scripts?
In response to Chad Birch's answer:
Yes, I'm referring to when developing a "standard" site that would employ AJAX for its benefits, and wouldn't be crippled by its application. Using AJAX in a way that would kill search rankings would not be acceptable. So if "keeping the site intact" requires more work, than that would be a "con".
It's a pretty large subject, but you should be using AJAX to enhance the user experience, without making the site totally dependent on it. Remember that search engines and some other visitors won't be able to execute the AJAX, so if you rely on it to load your content, that will not work in your favor.
For example, you might think that it would be nice to have users visit your blog, and then have the page dynamically load the newest article(s) with AJAX once they're already there. However, when Google tries to index your blog, it's just going to get the blank site.
A good search term to find resources related to this subject is "progressive enhancement". There's plenty of good stuff out there, spend some time following the links around. Here's one to start you off:
http://www.alistapart.com/articles/progressiveenhancementwithjavascript/
When you are only updating part of a page or perhaps performing an action that doesn't update the page at all AJAX can be a very good tool. It's much more lightweight than an entire page refresh for something like this. Conversely, if your entire page reloads or you change to a different view, you really should just link (or post) to the new page rather than download it via AJAX and replace the entire contents.
One downside to using AJAX is that it requires javascript to be working OR you to construct your view in such a way that the UI still works without it. This is more complicated than doing it just via normal links/posts.
AJAX is usually used to perform an HTTP request while the page is already loaded (without loading another page).
The most common use is to update part of the view. Note that this does not include refreshing the whole view since you could just navigate to a new page.
Another common use is to submit forms. In all cases, but especially for forms, it is important to have good ways of handling browsers that do not have javascript or where it is disabled.
I think the advantage of using ajax technologies isn't only for creating better user-experiences, the ability to make server calls for only specific data is a huge performance benefit.
Imagine having a huge bandwidth eater site (like stackoverflow), most of the navigation done by users is done through page reloads, and data that is continuously sent over HTTP.
Of course caching and other techniques help this bandwidth over-head problem, but personally I think that sending huge chunks of HTML everytime is really a waste.
Cons are SEO (which doesn't work with highly based ajax sites) and people that have JavaScript disabled.
When your application (or your users) demand a richer user experience than a traditional webpage is able to provide.
Ajax gives you two big things:
Responsiveness - you can update only parts of a web page at a time if need be (saving the time to re-load a page). It also makes it easier to page data that is presented in a table for instance.
User Experience - This goes along with responsiveness. With AJAX you can add animations, cooler popups and special effects to give your web pages a newer, cleaner and cooler look and feel. If no one thinks this is important then look to the iPhone. User Experience draws people into an application and make them want to use it, one of the key steps in ensuring an application's success.
For a good case study, look at this site. AJAX effects like animating your new Answer when posted, popups to tell you you can't do certain things and hints that new answers have been posted since you started your own answer are all part of drawing people into this site and making it successful.
Javascript should always just be an addition to the functionality of your website. You should be able to use and navigate the site without any Javascript involved. You can use Javascript as an addition to existing functionality, for example to avoid full-page reloads. This is an important factor for accessibility. Javascript should never be used as the only possibility to reach or complete a request on your site.
As AJAX makes use of Javascript, the same applies here.
Ajax is primarily used when you want to reload part of a page without reposting all the information to the server.
Cons:
More complicated than doing a normal post (working with different browsers, writing server side code to hadle partial postbacks)
Introduces potential security vulnerabilities (
You are introducing additional code that interacts with the server. This can be a problem on both the client and server.
On the client, you need ways of sending and receiving responses. It's another way of interacting with the browser which means there is another point of entry that has to be guarded. Executing arbritary code, posting data to a non-intended source etc. There are several exploits for Ajax apps that have been plugged over time, but there will always be more.
)
Pros:
It looks flashier to end users
Allows a lot of information to be displayed on the page without having to load all at the same time
Page is more interactive.
I have a doubt: -
Is there any standard/convention that when should I use "Smarty templating" and when should I use Javascript Ajax calls to produce the content? I can use Ajax/Javascript calls to produce the content dynamically.
My application uses both Ajax and Smarty, but I want to set a rule for developers
You should only use AJAX calls to load dynamic data that is not known at the moment the page is loaded. For example, when you click the "comments" link for a given question/answer on Stack Overflow, an AJAX call is made to dynamically load the data. This is a result of the user clicking the comments link, not a result of the page loading. You don't know that you should show those comments at the time the page is loaded, so it is appropriate to make an AJAX call in this case.
You should use templating to show any data that is known at the moment the page is loaded. It makes it easier to deal with people that have Javascript disabled (I know, not a lot), and it provides a clear separation of logic from presentation. Another important benefit of using templating is the fact that is can significantly decrease the number of HTTP requests made from the client's browser.
This is especially important in the mobile browsing world where latency, not bandwidth, is your biggest obstacle. In mobile Safari, for example, a single HTTP request to a Smarty-templated page will load significantly faster than a request to load a Javascript-templated page that makes five or six additional HTTP requests. This is especially true when using EDGE, 3G, and other non-wifi mobile data services. In fact, this is so important that it is the first guideline in Yahoo's Best Practices for Speeding Up Your Website.
Ideally, you should also gracefully degrade functionality when Javascript is disabled. A good example is an auto-completing search box. It's really cool to have suggested search terms magically appear as you type, but if you turn off Javascript, you still have a functional search box. That's a classic example of a good degradation in service. Stack Overflow generally does a great job providing a solid non-Javascript experience. One place it falls short is in the comments. When Javascript is disabled, only the most popular comments are displayed, and posting new comments is disabled.
Unless absolutely necessary, you should think of Javascript as a bonus feature that might not be enabled, not as something that should be used to construct critical pieces of your website. There are obviously exceptions (some things just can't be done without Javascript). You'll notice, for example, that Stack Overflow is very usable with Javascript turned off. You won't get the real-time updates when new answers are posted, or fancy real-time Markdown previews, but the core functionality is still there. All the "heavy lifting" is done with HTML and CSS. Javascript is just icing (admittedly very good icing) on the cake. This is kind of a side note, but it's important enough to mention.
It probably depends on what sort of work you are doing in your templates. Personally, I hate doing a lot of heavy style/layout stuff strictly in Javascript. If you can load the bulk of your layout via. Smarty and just change specific bits of data (just the data, not the markup/style, if possible) that might be a good place to start with for standardizing within your own developer team.
Use templates for server-side generation and DHTML/AJAX for anything after the original page load (not using a refresh). Even then, the server response for the AJAX call itself can be assembled with a template, which may work best for any non-trivial content.
For the following pretty straightforward task: query a list of products from a DB and present it on a webpage,
consider 2 setups:
Setup1: PHP script queries. All content is built on the server and the entire page is served back to the client.
Setup2: Static HTML "page skeleton" requesting content using AJAX. Received content is parsed on the client side using Javascript and rendered using innerHTML or similar.
Of course the second setup only makes sense when you have pages, categories and tags for the client user to choose from.
I need to compare these two, at least by means of:
time it will take content to be served
user experience (setup1 is delivered as a whole, setup2 is delivered in "two parts")
scalability - how do the setups compare when I have 100,000 queries daily
Any thoughts on the issue will be much appreciated.
You may find the following question helpful: Smarty Vs. Javascript/AJAX
I brought up a few points in my answer to that question:
You should use server-side scripts to show any data that is known at the moment the page is loaded. In this case, you know the list of products should be displayed. The fact that a question's answers should be shown is known at page load.
You should only use AJAX calls to load dynamic data that is not known at the moment the page is loaded. For example, when you click the "comments" link under a question or answer on Stack Overflow. The fact that you want to view a particular question's comments is not known at page load.
Javascript should not be required to access core functionality of your site.
You should gracefully degrade functionality when Javascript is disabled. For example, Stack Overflow works just fine with Javascript disabled. You don't have access to real-time Markdown previews or dynamic badge notices, but the core functionality is still intact.
A single HTTP request to a server-generated page will load significantly faster than a request to load a page that makes five or six additional AJAX calls, especially on high latency connections (like cellular networks). See Yahoo's Best Practices for Speeding Up Your Website.
You should think of Javascript as a bonus feature that might not be enabled, not as something that should be used to construct critical pieces of your website. There are exceptions to this rule. If you want to do some sort of pagination in which you click a "next page" button and only the product list changes, AJAX might be the right choice. You should, however, make sure users without Javascript are not excluded from viewing the entire list.
There's nothing more frustrating than when a page can't be accessed because the web developer didn't obey the KISS principle. As an example, take Friendly's Restaurants. I wanted to check out their menu while I was at the mall, so I loaded their website on my iPhone, only to find out that you literally can't get any meaningful information about the restaurant without Flash. It's nice to have fancy menus with swooshing desserts flying everywhere, but in the end, I just wanted to see the items on their menu. I couldn't do that because they required Flash. Graceful degradation in service would have been helpful in that case.
Some things on the web can't be done effectively without Javascript. Displaying a list of products is not one of them. If you are still unsure, look at how other popular websites do things. I think you'll find most of the successful, well-engineered websites follow the guidelines listed above.
AJAX is probably better choice when only a small part of the page changes.
I would recommend starting with the server side version and then building AJAX on top of that. This way you will get also a version of your site that works without javascript, which you probably need anyway if you care about being indexed in search engines.
But first concentrate on creating a page that just works - you can always optimize it later.
Performance on the client has many factors. What is running at the time, what browser, what the content is, what the CSS of the page is, how full is the browser's cache, what plug-ins are installed, what is happening on the network, etc. Just remember that when you are playing with the numbers.
Unless the implementation sucks, AJAX should win hands down. Among the benefits are:
parallelism due to parallel requests on the client side (i.e. you can use multiple server CPU cores to serve parts of one served web page, that can't be done easily using PHP)
refreshing only small parts of the page is faster (less data to transfer, generate ...)
it scales much better since the server has less work to do (esp. if you can offload some of the processing needed for generating html to the client instead of just delivering it)
Dynamic pages like http://www.startpagina.nl/ have been doing this successfully since way before the recent AJAX fad (1 static file delivered, all customization done on the client side - last time I checked anyway).
Of course you can screw things up with either method so that it becomes slower than the other.