I know from an historical perspective that it has always been frowned upon to not gracefully degrade when a visitor with Javascript disabled visits a site but how relevant is this now?
I'm asking since an application I'm building is going to make heavy use of Javascript for charting and user interaction with the charts.
Most of the most popular sites on the web are rendered more or less useless without it enabled. I can't even login to twitter without it enabled, core bits of Facebook stop working and trying to visit Google maps just redirects to their search home page.
The kind of interaction I'm planning would be next to impossible to do any other way, and even if there was a way there isn't the resources to develop two versions of things.
The problem I have is that the site also needs to be as accessible as possible. It's an inherently visual site which makes this problematic to say the least. I'm not even sure there is a solution to this particular problem. If it's visual it's not going to be suitable for blind people.
This depends entirely on your needs and what you want your demographic to be. A lot of sites use exclusively flash to silverlight; does that make them poorly designed? No. All it means is that the site caters to a very specific audience.
As long as you are accepting that there may be a (albeit) small populous that aren't going to use the site (or can't due to missing support) then it's fine.
Side-note: there are other means of conveying graphics other than javascript. Using server-side image generators is one way. You may also decide to use flash/silverlight plugins or activeX/applets. My advice would be to design the site as you see fit.
I would bet that the amount of javascript support these days is in the majority, so creating the site first then working on the discrepancies later wouldn't be a bad avenue. Youre still going to receive a high saturation of visitors just on the assumption that most clients support it.
Heck, look at sites using html5--it's not a standard, and no browser has to support it, but this still doesn't stop people from taking advantage of article, header & footer elements. Granted, there is html5shiv to gracefully down-grade it, but even that depends on JS being present.
Javascript has become so thoroughly integrated with web development that it is now users that browse without Javascript that have become a novelty.
What you should do is put up a friendly message that informs the user that the specific service your page provides (charts etc.) cannot be provided without JS enabled, and leave it at that.
What I would worry about is thoroughly detecting feature compatibility, because while people with JS disabled aren't that common, people with ancient browsers are.
Since you tagged this with accessibility, I will cover that perspective. As others have said, Javascript is part of something that we live with. While it isn't expected that the application can be made fully accessible to people with visual imparments, you have to keep in mind other disabilities as well such as mobility imparments. WebAIM has an article about what to keep in mind when you are coding JS events to make it as accessible as possible.
Depending on what these charts do, you should put the resulting data in an accessible table at the very least either somewhere on the page or a link to the data/table in proxcimity of the graph, so that it is easy to find for those who need it.
You didn't specify who you are making this for, so I will give some more information. Gez Lemon wrote an article about not using <noscript>, his summary is:
I'm surprised that the noscript element is conforming in HTML5, as there are much better techniques for ensuring that pages work with or without JavaScript. Despite early accessibility advice advocating use of the noscript element, best practice is to use unobtrusive JavaScript for progressive enhancement, rather than relying on fallback content.
This sort of echoes what I began my answer with. However, if you are doing this for a US or state government agency, you must still use <noscript> tags because it is a requirement of Section 508. The information with the <noscript> tags should be useful. EX:
<script type="text/javascript">
// Do something cool
</script>
<noscript>
Please perform your search again using the <a>javascript-free form</a>
to get the results in a table.
</noscript>
I have been developing web applications for a few years now. One of the issues that I face is having to develop web apps where javascript is not enabled or not available. I know this was a issue a few year back but am curious to know what other web designers, developers think about this issue? Is that still an issue?
The reason I am asking this is because it seems to me we are just catering for scenarios that is very unlikely to happen now a days. This is especially with regards to public facing websites and web applications? Am I right in my assessment? I am keen to know the experiences and any learnings of other web developers and designers
Thanks.
Even today, some people (including myself) have JS turned off by default. Professionally built sites either warn about disabled features or work without JS (via full page reloads).
I would recommend you try to ensure the basic functionality of your site is available without javascript.
If you work this way, you'll end up with a site that works even if you, or another dev, allows imperfect JS into the production site - a serious JS error won't necessarily be a total show-stopper.
Also: AJAX, effects and other fluff can take aaaaaaages to debug. Users don't mind simple. You should aim for simple, and slowly add bells and whistles, user testing as you add, to avoid creating an AJAXeffectsFluffy crap heap that is confusing and buggy...
+1 for Progressive Enhancement. This is where you have basic, non-flashy, functionality with straight-forward HTML/CSS then get JavaScript code to either supplement or replace that functionality with it's own.
For instance, if you have paging navigation on the page that consists of simple hyperlinks for page 1, page 2 etc eg.
<div class="paging">
<ul>
<li>1
<li>2
<li>3
</ul>
</div>
Then you'd have JavaScript functionality that looks for your div.paging element and completely replaces it with something more elegant, eg (in pseudo code)
$('div.paging').each(function()
{
$(this).find('ul').remove();
$(this).append(renderAdvancedPaging());
});
As for what it could be replaced by, it could be Google Images style infinite scroll (yes I know Bing had it first), or Twitter's approach of having a big next page button at the bottom that dynamically appends the next set of results (have a look http://twitter.com/codinghorror - scroll down and click 'More').
The benefits of this 'Progressive Enhancement' approach are:
Works for people who have disabled JavaScript, this includes savvy users, and users working in heavily locked down corporate intranets.
Accessibility: blind users with screen readers can still use your site.
Search engines, which won't execute any JavaScript on your page, can still follow your paging links and index additional content of those pages.
The last point should be the most important if you care about SEO.
There are times, however, when you can reasonably ignore Progressive Enhancement and build a website which relies on JavaScript and won't work without it. You'd typically do this for advanced 'Web Applications' or mobile optimised web-apps for instance, think Google Maps, a calendar app, a HTML5 drawing app that uses the <canvas> element, an HTML5 powered game etc. My rule, anything 'Content Based' (blogging site, news site, e-commerce shop etc.) should apply Progressive Enhancement, whereas anything 'Application-y' could just get away with mandating JavaScript.
Ultimately, it comes down to what you're building and whether the Progressive Enhancement route is right for you.
Stats for number of people with JavaScript disabled is hard to come by (some here but it's from 2008, also this StackOverflow post from 2008), but I think it's becoming increasingly less likely to have script disabled because of the increasing number of RIA apps and HTML5 apps that rely on JavaScript (Google Docs, Maps etc.). Also take into account the increasing number of Mobile Internet Devices (iPhones, iPads etc.) that don't allow you to disable JavaScript.
Progressive enhancement! I nearly always browse with JS disabled after spending way too long being annoyed by over AJAXd websites, so always start from simple page load forms etc before adding JS functionality.
JS frameworks like jQuery, mootools etc are getting more and more popular as pretty much anyone can produce a "shiny" website with animations. But I think that the more people start to use the tools, the less willing any regular browser will be to enable JS.
There are some who think you need to also take care of people who have CSS turned off. All this can drive you crazy, accounting for all the "what ifs" of the web world. Those who turn off javascript know what they are in for and are never surprised to find a site that doesn't work because of it. If they know enough to turn it off then they know enough to turn it back on when they need it.
I think it was Tim Berners-Lee who once said the web was always meant to be scriptable. Scripting hooks are built into HTML and all browsers work with it. Almost everyone has it turned on and they should. Use it to your advantage.
Is Graceful degradation possible for everything? for every javascript and javascript frameworks functionality?
No, it is not possible for everything. There comes a point when you have to decide if you can support a feature with or without javascript, or if it simply can't be done without it (or would take too much time/money to accomplish).
This concept might help you:
For public websites meant to provide information, make sure every essential piece works with/without JS. This includes sales sites, corporate information sites, business micro sites, etc.
If the site is a web application with tools available behind a login, then making JS a requirement makes more sense since you can notify the user of this requirement upon signup/signin. Obviously you should still go as far as you can to make the site accessible for handicapped users.
If you start with a non-javascript webpage, and get the functionality that you are willing to accept, then you can get graceful degradation to work, as you have a lower level that is acceptable, so if you can't get some functionality to work you can just not use javascript for that part.
But, if you absolutely require javascript then you need to decide on a least supported version, and get your app to work that way.
You may find that you will need to be able to replace some functionality that doesn't exist in the browser's version of javascript, so, if you use the string.trim() function but it isn't included, then you need to write it, and use the String.prototype functionality.
If you use unobtrusive javascript then you can test before making any changes to the dom elements to see what needs to be done to get that functionality to work.
If you find a framework that doesn't meet your needs, you will need to replace that framework with your own, rather than having a mix where on some browsers you have one framework and on others you have your own.
It depends what you will accept as functional, if you require a dialog box to pop up on the page and request user input, then no, but if it's ok that the page redirects to an input form then it is.
There are a lot of cool things that can be done with javascript, but with some thought things can usually be functional (but probably not pretty) without.
In my experience, I've yet to find a scenario that can't be solved with graceful degradation. Consider a "to-do list" app of today versus a decade ago. Today, if you would like to order a list of items, you simply drag & drop. A decade ago, you would click a "re-order" button, visit a second page where you would manually modify the IDs for each item for numeric sorting.
I tend to build apps (with a framework behind them, mind you) that already support this structure. Then, with "progressive enhancement" via Javascript, you can simply ease the user's burden in making these changes and still take advantage of the same code in the backend.
So yes, as long as a browser supports cookies for session data, an app can remain entirely functional without Javascript. It will simply be more difficult to use :)
Have you experimented with single page web application, i.e. where the browser only 'GETs' one page form the server, the rest being handled by client side javascript code (one good example of such an 'application page' is Gmail)?
What are some pro's and con's of going with this approach for simpler applications (such as blogs and CMSs)?
How do you go about designing such an application?
Edit: As mentioned in the response a difficuly is to handle the back button, the refresh button, bookmarking/copying url. The latter can be solved using location.hash, any clue about the remaining two issues?
I call these single page apps "long lived" apps.
For "simpler applications" as you put it it's terrible. Things that work OOTB for browsers all of a sudden need special care and attention:
the back button
the refresh button
bookmarking/copying url
Note I'm not saying you can't do these things with single-page apps, I'm saying you need to make the effort to build them into the app code. If you simply had different resources at different urls, these work with no additional developer effort.
Now, for complex apps like gmail, google maps, the benefits there are:
user-perceived responsiveness of the application can increase
the usability of the application may go up (eg scrollbars don't jump to the top on the new page when clicking on what the user thought was a small action)
no white screen flicker during the HTTP request->response
One concern with long-lived apps is memory leaks. Traditional sites that requests a new page for each user action have the added benefit that the browser discards the DOM and any unused objects to the degree that memory can be reclaimed. Newer browsers have different mechanisms for this, but lets take IE as an example. IE will require special care to clean up memory periodically during the lifetime of the long-lived app. This is made somewhat easier by libraries these days, but by no means is a triviality.
As with a lot of things, a hybrid approach is great. It allows you to leverage JavaScript for lazy-loading specific content while separating parts of the app by page/url.
One pro is that you get the full presentation power of JavaScript as opposed to non-JavaScript web sites where the browser may flicker between pages and similar minor nuisances. You may notice lower bandwidth use as well as a result of only handling with the immediately important parts that need to be refreshed instead of getting a full web page back from the server.
The major con behind this is the accessibility concern. Users without JavaScript (or those who choose to disable it) can't use your web site unless you do some serious server-side coding to determine what to respond with depending on whether the request was made using AJAX or not. Depending on what (server-side) web framework you use, this can be either easy or extremely tedious.
It is not considered a good idea in general to have a web site which relies completely on the user having JavaScript.
One major con, and a major complaint of websites that have taken AJAX perhaps a bit too far, is that you lose the ability to bookmark pages that are "deep" into the content of the site. When a user bookmarks the page they will always get the "front" page of the site, regardless of what content they were looking at when they made the bookmark.
Maybe you should check SproutCore (Apple Used it for MobileMe) or Cappuccino, these are Javascript frameworks to make exactly that, designing desktop-like interfaces that only fetch responses from the server via JSON or XML.
Using either for a blog won't be a good idea, but a well designed desktop-like blog admin area may be a joy to use.
The main reason to avoid it is that taken alone it's extremely search-unfriendly. That's fine for webapps like GMail that don't need to be publically searchable, but for your blogs and CMS-driven sites it would be a disaster.
You could of course create the simple HTML version and then progressive-enhance it, but making it work nicely in both versions at once could be a bunch of work.
I was creating exactly these kind of pages as webapps for the iPhone. My method was to really put everything in one huge index.html file and to hide or show certain content. This showing and hiding i.e. the navigation of the page, I control in a special javascript file where the necessary functions for handling the display of the parts in the page are.
Pro: Everything is loaded in the beginning and you don't need to request anything from the server anymore, e.g. "switching" content and performing actions is very fast.
Con: First, everything has to load... that can take its time, if you have a lot of content that has to be shown immediately.
Another issue is that in case when the connection goes down, the user will not really notice until he actually needs the server side. You can notice that in Gmail as well. (It sometimes can be a positive thing though).
Hope it helps! greets
Usually, you will take a framework like GWT, Echo2 or similar.
The advantage of this approach is that the application feels much more like a desktop app. When the server is fast enough, users won't notice the many little data packets that go back and forth. Also, loading a page from scratch is an expensive operation. If you just modify parts of it, the browser can keep a lot of the existing model in memory and just change the parts that changed.
Another advantage of these frameworks is that you can develop your application in pure Java. This means you can debug it in your IDE just like any other Java app, you can write unit tests and run them automatically, etc.
I'll add that on slower machines, a con is that a large amount of JavaScript will bring the browser to a screeching halt. Since all the rendering is done client-side, if the user doesn't have a higher-end computer, it will ruin the experience. My work computer is a P4 3.0GHZ with 2 GB of ram and JavaScript heavy sites cause it to chug along slower than molasses, which really kills the user experience for me.
It's fall of 2008, and I still hear developers say that you should not design a site that requires JavaScript.
I understand that you should develop sites that degrade gracefully when JS is not present/on. But at what point do you not include funcitonality that can only be powered by JS?
I guess the question comes down to demographics. Are there numbers out there of how many folks are browsing without JS?
Just as long as you're aware of the accessibility limitations you might be introducing, ie for users of screen-reading software, etc.
It's one thing to exclude people because they choose to turn off JS or use a browser which doesn't support it, it's entirely another to exclude them because of a disability.
Two simple questions to help you decide...
Does using javascript provide some
core functionality of your site?
Are you prepared to limit your
potential users to those who have
JS? (ie. Most people)
If you answer yes to both of those, go for it!
Websites are moving (have moved?) from static pages of information to interactive web applications. Without something like Javascript or Flash, making compelling user interactions is sometimes not possible.
Designing to degrade gracefully is the most that should be done. We are moving/have moved past the point of simple web "sites" to web "applications". The only option besides client side scripting to add round trips to the server.
I think (personal opinion) that the "don't use JavaScript" comes more from a lack of understanding of what JavaScript is/does than any actual market data that shows a significant number of people are browsing without it.
It's reasonable to design sites that use JavaScript but it is not safe to assume that all clients have support for Javascript and therefore it is important that you provide a satisfactory experience even when JavaScript is not available
Search Engines don't support JavaScript. They're also blind and don't support CSS. So my suggestion to you is to make sure that the part of your product that needs to be indexable by search engines works without JavaScript and CSS. After that, it really depends on the needs of your users.
If you have a very limited subset of users, then you can actually query them. But to remember that 10% of the population has some form of impairment ranging from vision issues (low vision, color-blindness, etc.) or motor functions (low hand dexterity). These problems tend to be more prominent in the elderly and the knowingly disabled
If your site will target the general audience of Internet users then please make it degrade gracefully, but if you can't do that, then make a no-JavaScript version (like G-mail has).
I think the days of "content sites only" are gone. What we see now is WWW emerging as the platform of web applications, and the latest developments in the browser front (speeding up JS in particular) ar indication of this.
There can be no yes/no answer to your question - you should decide, where on content site<---->web application continuum your site is and how essential is the experience provided by JavaScript. In my opinion - yes it is acceptable to have web applications which require Javascript to function.
Degrading gracefully is a must. At a minimum, you sure make use of the NOSCRIPT tag in order to inform potential customers first that your site requires javascript, and secondly why you require it.
If it's for flashy menus and presentations that I could honestly care less about then I probably won't bother coming back. If there's a real reason that you're requiring javascript (client-side validation on forms, or a real situation that requires AJAX for performance reasons) then say so and your visitors will respond accordingly.
I install extensions that limit both Javascript and Cookies. Websites that don't prominently state their requirements of both usually don't get a second visit unless there's a real need for it.
You should never design a public site to rely on ANY technology/platform. The user agent may not display colour (think screen readers), display graphics (again, think screen readers or text only browsers such as links), etc.
Design your site for the lowest common denominator and then progressively enhance it to add support for specific technologies.
To answer the question directly: No, you cannot assume your users have Javascript, so your site should work without it. Once it does, enhance it with Javascript.
it's not about browser capability, it's about user control. People who install the noscript plugin for firefox so they don't have to put up with punch-the-monkey garbage ( the same problem that inspired stack overflow) will not allow your web site to do anything non-static until they trust you.
In terms of client software consider users/customers who are using a browser that supports some but not all Javascript. For example, most mobile phone browsers support a bit of Javascript but nothing very complicated. The browsers on devices such as the Playstation 3 are similar.
Then there are browsers such as Opera Mini, which support a lot of Javascript but are operating in an environment where the scripts are running on a server that then sends the results to a mobile device.
You should design websites with Javascript in mind--but not implemented. Consider, build it where every click, every action, performs a round trip to the server. That's the default functionality for older browsers, and those without JS turned on.
Then, after it's all built, and everything is working properly, add in JavaScript which hijacks the link, button and other events, and overlay their standard functionality with the Javascript functionality you're wanting.
Building the application like this means that it will ALWAYS work, which ultimately is what you're wanting.
The received wisdom answer is that you can use JavaScript (or any other technology) providing that it 'degrades gracefully'...
I have experience with disability organisations, so accessibility is important to me. But equally, I'm in the business of building attractive, usable websites, so javascript can be a powerful ally. It's a difficult call, but if you can build a rich, javascript-aided site, without completely alienating non-js vistors, then do so. If not, you will have to look at the context of the site and decide which way to jump.
Regardless, there are no rights and wrongs with this question. However, in some countries, there is a requirement to build 'public' sites to be accessible, so this may be yet another factor in your decision. [In the UK, it is the Disability Discrimination Act.. though to my knowledge, no company has been prosecuted for failure to comply]
JavaScript is great for extending the browser to do things like google maps. But it's a pointy instrument, so use it with care.
My bank web site uses JavaScript for basic navigation between pages. Sigh. As a result, it's not usable from my mobile device.
Make sure you're familiar with the Rule of Least Power when considering JavaScript:
When designing computer systems, one
is often faced with a choice between
using a more or less powerful language
for publishing information, for
expressing constraints, or for solving
some problem. This finding explores
tradeoffs relating the choice of
language to reusability of
information. The "Rule of Least Power"
suggests choosing the least powerful
language suitable for a given purpose.
5% according to these statistics: http://www.w3schools.com/browsers/browsers_stats.asp
As you said, demographics. The web is expanding onto devices that doesn't have very much power, for instance cellphones. If your site is usable without javascript, Opera Mini will likely show your site without any problems.
I think Javascript implementations in most modern browsers have now reached a reasonable level of maturity and there are a bunch of Javascript UI frameworks which let you build very attractive Javascript based web applications using web-services and such (regardless of the back-end server platform).
An example is ExtJS - they have got a very extensive AJAX + UI widget framework which I recently used to build a full fledged internal web-app for a client with an ASP.NET backend (for webservices).
I think it comes down to what you're about to do. Are you writing a web APPLICATION? Then I think you're bound to use javascript and/or something like GWT. Just have a look at all the social sites, and google aplications like gmail. If you're writing a webpage with product descriptions and hardly any interactivity, then you can make the javascript optional.
I agree with the majority of the stackoverflow respondents. JavaScript has matured and offers an "extra" level of functionality to a webpage, especially for forms. Those who turn off cookies and JS have likely been bitten while surfing in dangerous waters. For the corporate power users that pay my way either in B2B or retail sites, JS is a proven and trusty tool. Until something better comes along (and it will) I'm sticking with JS.
There's addon for Firefox called NoScript which have 27,501,701 downloads. If you site won't work without JavaScript most of those guys wouldn't want to use it.
Why you would install that addon? Ever wanted to get rid of the popup on the site that cover the most of the useful text you want to rid? Or disable flash animation? Or be sure that evil site won't steal your cookies?
Some corporate environments won't allow Javascript, by policy or by firewall. It closes the door to one avenue of virus infection.
Whether you think this is a good idea or not, realize that not everyone has full control over their browser and it might not be their choice.
There is a gradient between web sites and web applications. However, you should alway be able to say "we are building a web site" or "we are building a web application".
Web sites should be readable down to plain HTML (no CSS, no images, no JavaScript).
Web applications, of course, could just say "Sorry, JavaScript is needed" (which also assumes CSS for layout). Application should still be able to work without images.
The accessibility issue is the only important technical issue, all other issues can be socially engineered. When one says that javascript reduced accessibility and another says that Web Applications can use javascript, can we take these two together to imply that all blind people are unemployed? There has to be some kind of momentum in making javascript accessible. Maybe a Screenreader object on the javascript side which can detect the presence of a screenreader and then maybe send hints to the screenreader, Screenreaders which can hook onto the browser, and maybe it gets glued together with a screenreader toolbar.
if you want your site viewable by the top 100 companies in the US. I would write without javascript.
Independence from Javascript and graceful degradation are important to an application despite the actual demographics -- because such an application probably has better software design.
The "human user without Javascript" may be purely hypothetical (for example, if you're trying to make money with your product). But designing for that hypothetical user encourages modular software design which will pay off as you continue to develop your app.
Javascript provides functionality. HTML provides data (on the page itself, and via links that point to more data). As a general rule that reaches well beyond browser apps: A well-designed software product will separate data from functionality. All data should be available, and the functionality should be a separate layer that consumes the data.
If your Javascript is creating data at runtime, then it's time to get specific and figure out whether your webpage really is a piece of software (e.g. a mortgage calculator) or whether it's a document containing data (e.g. a list of mortgage interest rates). This should tell you whether it makes sense to rely on Javascript.
As a final note/example, demographics can be misleading. Relatively few humans browse your site without Javascript, but lots of machines (search bots, data miners, screen readers for the disabled, etc.) are browsing your site without Javascript. Again, the distinction between data and functionality are important -- the bots are just making requests and looking for data in the responses. They don't need functionality. But if your user needs to invoke functions just to make your data accessible, the bots are getting no value from your site.
One side point about the screen readers and other accessibility considerations for the disabled. This is an important niche demographic: a mind that navigates data in a human way, but who can only get data from your site in the same way machines get it. By providing data cleanly and semantically on your page, you make it available to the largest possible set of accessibility tools.
Note this doesn't exclude Javascript from consideration. Our mortgage calculator example can still work: accept input from the user, invoke Javascript, and write the output back into the clean semantic data layer of the page. Screen readers can then read it! And if they can't, you're encouraging the development of better screen readers that can.
If you expect your app to work for everyone, you'll need a backup for all your javascript functionality. If it's form validation, you should also check the data on the server before saving it. So the answer is Yes, it's okay, but have a backup. Do not rely on it.
As many people are saying, it's important to consider your user base, but whoever your users are there's a strong possibility that some (stats say 10%) of them will have some sort of disabilities, and screen readers don't like javascript. If you're only adding simple things, a javascript menu or something, then just make it degrade (or don't do it). If the site depends on javascript to work properly, make two versions, one for javascript and one without.
I generally find that anything too javascript heavy is very difficult to make degrade well without just having javascript re-writing the page to a javascript version if the user can take it. Given this, it's well worth writing two pages from square one for complicated stuff.
I would say that there are very very very few web sites that should be running without some support for users without javascript. You'd need to have a very dynamic application that completely didn't make sense as static pages,or you'd need to have a audience you could guarantee were ok with it (like on an office Intranet say).
Well, it depends on your userbase. If you know that people will be using your site from mobile devices, it's good to have unobtrusive JavaScript. However, if you're trying to appeal to a tech-savvy crowd, don't bother with it.
However, if you're appealing to a crowd that may be using screen readers (blind people), I'd highly suggest using WAI-ARIA standards. Dojo's widget system has full support for this, and would be a great and easy way to do it.
Anyway, in most cases, you don't need unobtrusive JavaScript. Most people who have JavaScript disabled are either using a smartphone, using Lynx, or have NoScript installed. It's enabled by default in all the major browsers, so you shouldn't have to worry.
Lastly, it's good to at least have some unobtrusive JavaScript. <noscript> tags are your best friend. For example, one may want to replace a widget that draws rating stars with text. Example using dojo:
<div dojoType="dojox.Rating" stars="5" value="4"></div>
<noscript>4/5</noscript>
It's the 21st century. People not permitting JavaScript need to exit the last millennium, posthaste. It's a mature, widely used, and very useful technology that is one of the foundations of the recent expansion in useful web services.
You should be tying the functionality of your website to your audience. That being said, every modern browser (save for the mobile platform) includes javascript, and so unless your audience includes luddites with decade old computers, you can assume they have javascript.
The people you need to worry about, then, are those that specifically turn it off. This includes:
Corporate networks with tough security (not common, but some financial and defense institutions)
Paranoid web-heads
So, first, who is your audience? Are there other websites that are comparable to your target? Look at their site and success - do they degrade gracefully, and would yo be satisfied with their level of success?
If you are targeting mobile applications, though, you can't guarantee javascript.
-Adam
I would say that you should look at your target audience. If you can reasonably expect that they will have js enabled, and making everything work without any js is too much of a pain, then by all means - go ahead and ignore the non-js crowd, if, on the other hand you have to create a site that will be used by a very large audience/or you are perhaps building a government web site, then you must make sure that everything works, and it is easier in those cases to first build the site so that it works without any js, and add all the nice time-saving ajaxy bits later.
In general though, almost everyone has js enabled by default.
Though you should be aware that server-side validation of user posted data is a must in either case.