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Javascript & jQuery - How much are we supposed to be using?

This question has been asked before, but I would like a little more detail from this one, more about the audience and why.
I was never a Javascript fan, if I could avoid using it I would... but now jQuery has evolved, I've found myself using a lot of it, and really enjoying it. But I now feel I could get carried away and use too much.
1) How many people actually have JS disabled? Does anyone have precise visitor statistics/analytics that proves what percentage of visitors are disabled? If it's only 1 - 5%, should we really be caring about them?
2) What's the reason for disabling JS in the first place, seeming as it's enabled by default on all browsers? I don't understand why the browser gives us that option. I've never found a reason to switch off my JS, unless it's for testing purposes.
3) Do you think that JS will ever become a permanent browser language, by disallowing users to switch it off? Websites would be amazing (and secure) if scripts were permanent.
M application, a secure login only site, is rich with AJAX, overlays, tooltips and elements fading in and out - so much that it wouldn't work without it. But this isn't a problem for me as my users are warned at the point of registration that JS is a 100% requirement and my particular visitors actually need my application. I also have a <noscript> redirection back to the login page.
I'm asking the above questions because I'm about to redevelop the home-page to my application, which is public, but I'm unsure about how much to use and how big the audience is that would miss out on the jQuery goodness.
Thanks

1) I found this blog post from Yahoo that states that around 0.25 and 2% of their visitors have JavaScript disabled.
2) I think this is a leftover from 10 years ago. There is no reason to disable JavaScript as the usability hit you take on many websites (with some not even being usable) is a lot more than the little security you gain. I always stretch that if non JavaScript users are that important to you then create a separate version of the page.
3) I don't know what you mean with permanent. JavaScript already runs in a Sandbox so you e.g. can't access local files. Other security issues are more things like secretly submitting forms or redirecting to a malicious page.

It depends. If I'm making a 'general' website you should account for no JavaScript, slow JavaScript and poor JavaScript (like IE6). Another thing to keep in mind are mobile devices.
If I'm making a JavaScript application with heavy use of AJAX and other modern web techniques I don't even bother.
In some situations it's easier to demand availability of JavaScript.

1) The more important figure is what percentage of your users/visitors don't have javascript, and whether or not you think the extra development cost (if there is any) of any fallbacks you might need is worth it. As said earlier, it depends on your situation
2) To stop popups, annoying scripts that change browser behaviour (such as disabling the right mouse button), and such

Website doesn't work with Javascript turned off

So head to www.jabsy.com, with Javascript turned off.
Basically, I use some JQuery UI Dialogs, I use Javascript for all the bindings on the page...I pretty much use it for everything. Is that really a bad thing though?
Nothing really works without Javascript. Not even the Google Maps API.
Should I go out of my way to try and make the entire page work without Javascript? Is that even possible with my site? I wouldn't even know where to begin as I use Javascript for everything, so could I get some points? How many users actually turn off their Javascript these days?
Would it help to let the user know if they have Javascript turned off and make them turn it on before accessing it and provide them with directions how?

Yes, if your site requires JavaScript you need to let the user know that it is required.
For example:
<noscript>
<div>
You need to have JavaScript enabled to use this site.
</div>
</noscript>
You can provide more description as appropriate. A savvy user that sees this text is going to be able to then go in and turn on JavaScript for your site. A non-technical user might have trouble, but I would think most of them would be running with JavaScript enabled anyway (?).

According to data collected in 2007, about 3% of users in the US have JavaScript off. I'm sure that number is lower today.
It really depends on how critical the sections of your page that require JavaScript are. If there is a form that is mission critical, but controlled completely by JavaScript, you probably want to engineer a way for that form to do the same thing with JS on and off.
However, you have animated snowflakes on your background (for the love of God, don't really do this), it's not going to negatively affect someone visiting your site with JavaScript off.
Really, it all comes down to how important the information or actions are to your site. Turn off JavaScript and note all the things you can't do that are absolutely vital, then make them work.
Keep in mind there are several audiences that will not render your JavaScript:
Screen readers/accessible browsers
Console-based browsers (Text based browsers)
Search Engines (Google)

Your specific service (location-based messages) will be way too cumbersome to use without JavaScript (and its content is dynamic). Therefore, I see no problem requiring it. You should, however, point out that JavaScript is necessary to use your site (Preferably at the top, in really large letters). You can do that by including the alternative no-JavaScript content in noscript tags, i.e.
<noscript>
<div style="font-size: 200%;">You need JavaScript!</div>
</noscript>
However, most websites are content-based, like a company's homepage, stackoverflow or Wikipedia. These websites should be usable without JavaScript. Nowadays, even smartphones have excellent JavaScript support, but Kindle and regular phones are still too slow for JavaScript.

There is a line of argument that says sites should work without JS. Personally, I think that is tosh, unless you have a clientelle for whom this is liable to be an issue. JS is a reasonable thing to expect for many sites.
However, it is polite to let people know that this is a requirement, and inform them rather than just letting it not work. If your site is heavily JS dependent, then you may have made some mistaken design decisions, but it is probably not worth re-working it. If you monitor the number of people who get the "you need js" message, you will identify if it is proving a turn-off. I suspect it will not be an issue.
So build based on what you need, BUT tell people if they need to have things set.

You can use the <noscript><!-- html here if no Javascript --></noscript> tags and place content to be rendered in between if javascript is turned off.
I don't think there are many sites that will work with these days without it. It's more or less mandatory.

Is graceful degradation in the absence of JavaScript still useful?

When even mobile browsers have JavaScript, is it really necessary to consider potential script-free users?

Yes. Your web pages aren't just consumed by people: they're consumed by search engines, and crawlers, and screenscrapers. Most of those automatic tools don't support Javascript, and essentially none are going to generate UI events or look at deeply nested AJAX data. You want to have a simple static HTML fallback, if nothing else then so that your web pages are well indexed by the search engines.
Forget the crazies who disable Javascript; think of the robots!

Yes.
People can (and do) browse with javascript disabled. If your site will work without users having to explicitly enable javascript for you, that makes them happy.
Exactly how relevant depends on your target audience, of course.

I would argue that you shouldn't go significantly out of your way to accommodate for non-JS users for the following reasons:
All Modern Browsers Support JS
This is a snapshot of browser usage
today:
http://www.w3schools.com/browsers/browsers_stats.asp
Even the oldest common browser, IE6,
supports basic JavaScript and AJAX.
If you decide not to integrate
certain features b/c of a JS
dependence, this proves that you are
essentially doing it for people who
started with JavaScript enabled and
explicitly chose to disable it. I
think these people should expect for
some features, and perhaps even
entire sites, not to work as a
consequence.
Few People Willingly Disable JS
Building on my point above, average
web users don't know or don't care
that JS can be disabled in browsers.
It's largely a tech savvy crowd who
knows how to do this (myself
included), and as tech savvy users we should know when to
turn it back on as well.
Cost of Support
In light of the above, consider that
choosing to accomodate users who have
primarily willingly disabled JS comes
with a very real cost. If you are
managing a large project with heavy
UI requirements, you can easily burn
a lot of developer hours
accommodating for what is a very
small user preference. Check your
budget. If it is going to take 2 devs
working 40 extra hours each on the project
to accomplish this feat, you are
easily going to burn a few thousand
dollars on what is essentially a
non-issue for the vast majority of
your users. How about using that time
and investment to further buff up
your core competency?
Precedence
I may very well be wrong on this, but
I think it would be difficult to find
major media or social sites that
don't rely on JavaScript for some
portion of their functionality to
work. If major businesses that rely
on the operation and accessibility of
their site to stay in business aren't
doing it, there's a good chance it's
because it isn't needed.
CAVEATS:
Know your market. Continue to build XHTML/CSS that is semantic (preferably by using the RDFa W3C recommendation). Still strive to make your sites accessible to the visually impaired. Don't believe everything you read. ;)
DISCLAIMER:
My argument above is largely dependent on how you define "graceful degradation." If you mean all the links still work, that's one thing, but if you mean all the links still work and so does the wombats game, that's another. I'm not trying to argue for making your site so JS dependent that non-JS users can't access any portion of it. I am trying to make an argument for the acceptability of certain features, even some core features, being reliant on JS.

It is relevant and it will be relevant even after 10-20 years when javascript might be supported everywhere. making things work without javascript is important development technique because it forces you to keep things simple and declarative. ideally javascript should be used only to enhance experience but your website shouldn't depend on it.
there is clear advantage from maintenance point of view to have most of the code in declarative format (html+css) and as little as possible in imperative (javascript).

My position:
I browse with NoScript, so if I come on your site it will be without benefit of Javascript. I don't expect the full user experience.
What I want, before turning on JS, is to be assured that you're reasonably competent and not malicious, and that I actually want what you're using JS for.
This means that, if you actually want me to use your site, you should allow me to look around, using links. (If I see a site that's totally useless without Javascript, I generally think the designers were incompetent.) You should let me know what sort of functionality I'll get from enabling Javascript, and you should present the site in a legitimate-seeming way.
I don't think that's too much to ask.

graceful degadation / progressive enhancement / unobstusive javascript is absolutely relevant!
as with all accessability issues: just imagine for one second what it's like to be the one on the outside who can't use the page.
imagine you're travelling around the world, you're in some hotel or internet café with really old computers, old software, old browsers, you want to look up your flight and you realize you can't because of some javascript incompatability in the old browser you're using.
(try 'old mobile phone' or 'stuck behind a corporate firewall' for different scenarios)
image what a world of possibilities opend up to blind people with screen readers and the web, and image what it's like to find these possibilties closed again because of javascript.
so much for appealing to your better nature.
you might also want to do it
to keep your site accessibly for search engines.

Yes, it's relevant. Mobile browsers in use today do not all have Javascript enabled. It's available on new phones, sure. But there are millions and millions of people like me, who have phones running older browsers, and for all of us, a JS-required browsing experience is just plain broken.
I don't even bother visiting sites that didn't have progressive enhancement in mind when they coded. I'm not technically behind the times. My phone is a year old. But I'm not going to re-up my contract and buy a new phone because of a crippled web experience.

It depends on who your target audience is. I have JavaScript turned off by default and turn it on when I know what the site's intent is.

It's generally much faster to browse with Javascript disabled (digg.com is lightning without JS), which is why it's popular.
In Opera it's really easy: you simply press F12 and untick the javascript option. I always browse without Flash, Java (not javascript), animated images and sound. I enable Flash on a per-site basis, eg YouTube. Sometimes I turn off JS temporarily if my system is slowing down.
And don't forget about:
Screen readers (I think they mostly have JS disabled)
Text browsers or other very old systems
Ad blockers (if your filename happens lands under their radar)
Any old browser that either doesn't support JS at all or the JS breaks (e.g. IE6 doesn't support some modern JS stuff).
The solution is to use progressive enhancement rather than graceful degradation, i.e. start with the basic HTML and add CSS. Then add Javascript and/or AJAX to parts of the site.
For example, if you had a site like Stack Overflow, voting up an answer could submit a form normally. If JS is enabled, it would do an AJAX request, update the vote count and cancel the form submission, without leaving the page. SO doesn't do this though...

I for one always have NoScript turned on unless I trust the site for a number of reasons including cross-site-scripting, click jacking, and HTML injection. It's not me being paranoid, it's because I know a lot of developers, and know most of them have no idea what web security is, never mind how to avoid vulnerabilities.
So until I trust a site there's no chance I'd let it do anything fancy.
For the unfamiliar, there are some interesting blog entries on the subject:
Protecting Your Cookies: HttpOnly
Cross-Site Request Forgeries and You
Sins of Software Security
Top 25 Most Dangerous Programming Mistakes

I'm going to have to make a case for the other side here. Peoples reasons for designing sites without javascript are largely idealistic. Given an enough time and money and the goal is achievable and will certainly open your website to the largest possible number of people. However in reality doing this will slow your development, increase the number of test cases that you have to deal with, and ultimately affect the quality of your application for those users that do use javascript.
In my opinion it is perfectly reasonable to choose to make your site only compatible with js enabled browsers and tell those users that dont have it that they are missing out. This allows you to concentrate on creating rich content that the majority of users will be able to view.
There are of course exceptions to this rule, but if you are looking to create a good website for the majority of users, or have a client who is after a flashy website with limited time or money then taking the decision that it is js enabled browsers only is a reasonable thing to do.

The real question is not whether it is relevant, but whether to use Graceful Degradation, or Progressive Enhancement as your scripting strategy.

I'm actually in an interesting position when it comes to graceful degradation of JS. I'm working on a web application that bots and crawlers have absolutely no business looking into. There's nothing they can gleam that should be indexed.
The informational site accompanying the web application, however, should be indexed, and therefore JS degrades gracefully there.
In the web application, if you don't have JavaScript enabled, you're probably not supposed to be there. It's intended to be a rich interactive experience. The web application actually requires JS to be enabled, and for you not to be sitting behind a corporate firewall.
We're not serving anything malicious, its just our intent and purpose for the web application that's different. The goals of our web application and those of our informational site are completely different.

I use JavaScript. I always keep my browser up-to-date. But sometimes, my Internet connection is so bad that scripts just don't load.
There are also cases when:
Some scripts load, but others fail, in which case parts of a website stop functioning
Scripts are loading, but I want to hit "submit" without waiting for that fancy frilly menu
A script malfunctions because it was partially loaded and then cached at that half-stage
I'm in such a hurry that I just decide to use Lynx.
Now, I'm not saying my Internet is bad all the time, or even most of the time, but it does happen. With the Internet expanding rapidly to many rural areas across the world, I'm sure I'm not the only one. So apart from bots as Nelson mentioned above, it's another thing to keep in mind. (Hint: check your demographics).

If you don't want the page to work when Javascript is off then just have that be the message in html, and if javascript is on, by using unobtrusive javascript you can get rid of that message and make visible the rest of the application.
Depending on what you write for, in terms of javascript version, you may need to degrade if the browser the user has doesn't not have the latest version, so gracefully handling that is also important.

Should your website work without JavaScript [duplicate]

This question already has answers here:
Do web sites really need to cater for browsers that don't have Javascript enabled? [closed]
(20 answers)
Closed 9 years ago.
We're developing a web application that is going to be used by external clients on the internet. The browsers we're required to support are IE7+ and FF3+. One of our requirements is that we use AJAX wherever possible. Given this requirement I feel that we shouldn't have to cater for users without javascript enabled, however others in the team disagree.
My question is, if, in this day and age, we should be required to cater for users that don't have javascript enabled?

Coming back more than 10 years later, it's worth noting my first two bullet points have faded to insignificance, and the situation has improved marginally for the third (accessible browsers do better) and fourth (Google runs more js) as well.
There are a lot more users on the public internet who may have trouble with javascript than you might think:
Mobile browsers (smartphones) often have very poor or buggy javascript implementations. These will often show up in statistics on the side of those that do support javascript, even though they in effect don't. This is getting better, but there are still lots of people stuck with old or slow android phones with very old versions of Chrome or bad webkit clones.
Things like NoScript are becoming more popular, so you should at least have a nice initial page for those users.
If your customer is in any way part of the U.S. Goverment, you are legally required to support screen readers, which typically don't do javascript, or don't do it well.
Search engines will, at best, only run a limited set of your javascript. You want to work well enough without javascript to allow them to still index your site.
Of course, you need to know your audience. You might be doing work for a corporate intranet where you know that everyone has javascript (though even here I'd argue there's a growing trend where these sites are made available to teleworkers with unknown/unrestricted browsers). Or you might be building an app for the blind community where no one has it. In the case of the public internet, you can typically figure about 95% of your users will support it in some fashion (source cited by someone else in one of the links below). That number sounds pretty high, but it can be misleading; turn it around, and if you don't support javascript you're turning away 1 visitor in 20.
See these:
https://stackoverflow.com/questions/121108/how-many-people-disable-javascript
https://stackoverflow.com/questions/822872/do-web-sites-really-need-to-cater-for-browsers-that-dont-have-javascript-enabled>

You should weigh the options and ask yourself:
1) what percentage of users will have javascript turned off. (according to this site, only 5% of the world has it turned off or not available.)
2) will those users be willing to turn it on
3) of those that aren't willing to turn it on, or switch to another browser or device that has javascript enabled, is the lost revenue more than the effort to build a separate non-javascript version?
Instinctively, I say most times the answer is no, don't waste the time building two sites.

My question is, if, in this day and age, we should be required to cater for users that don't have javascript enabled?
Yes, definitely, if the AJAX functionality is core to the working of your site. If you don't, you are effectively denying users who don't have Javascript enabled access to your website, and although this is a rather small proportion (<5% I believe), it means that they won't be able to use your site at all, because the core functions are not available to them.
Of course if you're doing more trivial things with AJAX that just enhance the user experience but are not actually central to the core functionality of the site, then this probably isn't necessary.

Depends really.
I personally switch off JavaScript all the time because I don't trust lots of sites.
However, since you users have explicitly asked for your application, you can assume they will trust it and there is no point in doing extra work.
More, if you have that strong AJAX-affinity requirement, the question seems odd enough.

This is a bit like beating a dead horse, but I'll have a go at it, sure.
I think there could be two basic approaches to this:
1.
Using ajax (and, basically,
javascript) to enhance the experience
of the users, while making sure, that
all of the application's features
work without javascript.
When I am
following this principle, I develop the
interface in two phases - first
without considering javascript at all
(say, using a framework, that doesn't
know about javascript) and then
augment certain workflows by adding
ajax-y validation (don't like pure js
validation, sorry) and so on.
This means, if the user has javascript disabled, your app shall in no way break or become unusable for him.
2.
Using javascript to its fullest, "no javascript - no go" style. If javascript is not available, the user will not be able to use your application at all. It is important to note, that, in my opinion, there is no middle ground, - if you are trying to be in both worlds at once, you are doing too much extra work. Removing the constraints of supporting no-javascript users, obviously adds more opportunities to create a richer user experience. And it makes creating that experience much easier.

I think that depends on the type of web application you are going to build. For example in an e-commerce application the checkout process should propably work without java script because there are some people who deactivate js for checking out (in our experience). In a web 2.0 application in my opinion it isn't necessary to support non-js browser experience.
Developing for both also complicates the development process and is more cost intensive. you have double your web test efforts (testing with and without js) and also think different in the planning phase.

I think it depends on the market segment you're aiming for, if you're going for a tech crowd -such as Stackoverflow.com, or perhaps slashdot- then you're probably fine in expecting users to have JS installed and active.
Other sites, with a medially tech-aware audience, may suffer from users knowing enough about JS-based exploits to have deactivated JS, but with not enough knowledge to enable Scriptblock (or other browser-equivalent).
The non-tech aware audience are probably with the tech-crowd, since they possibly just don't know how to disable JS -or why they may want to- regardless of the risk.

In short, you should cater to spiders without JavaScript enabled, but only to the degree necessary to index the data that you want to expose to the public. Your browser requirements of IE7+ and FF3+ exclude far more people than the total number of people who disable JavaScript. And of those who do disable it, the vast majority know how to enable it when necessary.

I asked myself the same question the other day and came up with the answer that in order to use my application one must have Javascript enabled. I also checked various Ajax powered sites. Even Stackoverflow.
But considering this fact I also believe that you do need to support some degree of prehistoric applications. The main idea is to not let application break when users don't have enabled Javascript. Application should still display relevant data, but its functionality would be limited.

To add to some of the old discussion on this page. Google is now searching JavaScript: http://www.i-programmer.info/news/81-web-general/4248-google-now-searches-javascript.html

This is an issue that I was thinking about just a few days ago. Here is some information
In Google Chrome there is no way (menu/option) inside the browser to turn off Javascript.
Many websites including those from leading names like Google, etc., will not work without Javascript.
According to stats over 95% of visitors have Javascript enabled now.
These stats made me think. Do I have to break my back writing a lot of background code and everything for users who have disabled Javascript?
My conclusion was this. Yes, I have to include Javascript support, but not at the cost of sanity. I.e. I can afford to give it a low priority.
So I am going to have support for non-javascript browsing, but I will build most of it after my site is deployed.

Why is JavaScript considered bad by some? [closed]

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Why is JavaScript allowed to be disabled in the browser? (i.e. Why is it considered bad?)

<body onload="for(i=0; i<1000000; i++){window.open(
'samplesite.com?pageid=' + i);}">

Why is javascript allowed to be disabled in the browser? (i.e. Why is it considered bad?)
Because it can be grossly misused (blinking images, anyone?), may slow the browser down and of course there's always the (very justified!) fear of exploited security holes.

First of all with Javascript you can create events that the user might not want you to, like e.g. changing the size of the window...
On the other hand think about people who are somehow limited... What if your user was blind and uses a screenreader while your page continously changes its content somehow... There are many reasons against Javascript when it comes to accessibility...

Back in time, it used to be:
A source of annoying cursor-following animations (I am sure you remember stuff, like raining sheeps or clocks following your cursor... I want to find the smart*** who thought of that and slap them with a trout)
Considered insecure
Served no purpose but bog down the browser
However, over the years it has become more advanced and applied with more thinking behind it.

Historically it has been a huge security problem for web based services. Also with any technology that is exploitable and has a low technical barrier for entry it ends up the tool of the low brow trouble maker (script kiddies). Quick searches for javascript or xss in a security exploit database will show hundreds of pages of vulnerability.

JavaScript is often considered dangerous or at least annoying for two reasons:
Websites can suddenly do stuff that you don't want them to do, e.g. open popups
Websites can suddenly keep you from doing stuff that you want to do, e.g. disabling right-clicks
Now, in the vast majority of cases JavaScript is harmless and can really enhance the user experience (Ajax comes to mind). But all it takes is one malicious site that uses JavaScript to do evil (TM) things like Cross-site Scripting. For that reason it is commonly considered best practice to disable JavaScript globally and to allow it for just those sites or domains that you explicitly trust. In this day and age being paranoid on the Internet is actually a good thing.

It's a weakly-typed scripting language. Programmers who usually use "big strong" languages look down upon such nonsense. Shame on you for even considering using it, and my God have mercy on your soul.

It can cause security problems. Especially in old versions of IE (not so much anymore).
Or maybe it has something to do with Stallman's ranting ;-)

The main consideration is security. Drive-by downloads that exploit browser security holes via JavaScript are currently the most common way for malware to spread.

As well as what others have said it confuses search engines. The more 'dynamic' content you add the higher the chances it cannot be indexed. In addition the Internet is used by many as a reference library. Books in a real library do not change things around while you are reading the page. You may think of your site as an "application" but your users may prefer to treat it as a "document".
In short JavaScript obfuscates information, sometimes to the point of completely denying access (i.e., the JavaScript code is buggy and crashing). A classic example of this was that I was unable to watch the Live8 concert broadcast by AOL a few years back because the JavaScript code was so poorly written it didn't actually work on my girlfriends' AOL browser (ironic I know). I tried to get to the movie URL directly but the obfuscation was so complex I couldn't find it. It did nothing to endear me to AOL.
BTW, I happen to be one of those people who disable JavaScript by default. If I need it I can enable it for a specific site or page in 2 seconds (really) using the NoScript add-on for Firefox.

Some companies, or business units, have a policy of not allowing javascript turned on, as there are concerns about any risk of security exploits, and that may be the biggest problem, that since it can't be locked down securely then it must be disabled. If you can run javascript in a strict mode, that doesn't allow ajax requests, for example, then you may find that more people are willing to use it on computers that are concerned about security.
As long as a user can go to a website, and information can be sent transparently over the Internet regarding what a user is doing, then these security concerns will exist.
For example, I could have a Firefox plugin that appears to be useful, but, it can do possibly send unwanted info to a website.

Because it shifts load from the server to the client and there is no way to control to what extent.
I work with Javascript every day and respectfully acknowledge what it has made possible, but sometimes when I browse a very simple page, and the interface reacts lightning fast because there is nothing to render but pure, simple HTML, I think that that used to be the original purpose the purpose of the internet. You can, and I am exaggerating only little, browse these pages with a 600 MhZ Pentium with 128 megabytes of RAM without problems. While for a Javascript-heavy, effectful "rich" website, you need massive resources on the client side for a halfway smooth experience, and you need to update your equipent almost as often as gamers do.
Also, I generally feel some, not hostility, but slight annoyance towards Javascript because it massively increased development costs by adding a host of incompatible target platforms, version, obscurities and specialties to cater for, as well as a generally bug-prone, hard to debug and volatile environment to work in.
That said, I think the industry owes the creators of JQuery, Prototype and the likes big, big thanks, among many others.

JavaScript, as the inventor of JSON called it, is the virtual machine for the world. It's where billions of people are. This great exposure comes with some dangers other languages do not have to face.
Example. Write a site that just 'redirects' you to another site, where you can sign in. If you are not completely in control of your browser/URL etc. some JavaScript just could have loaded the page content from another site and will log your keystrokes. This could be achieved with a few lines of JavaScript. It's not really the fault (if it's a fault at all) of JavaScript, but all the components (browser, HTML, and this vast space, we call Internet).

Why is javascript allowed to be
disabled in the browser? (i.e. Why is
it considered bad?)
Because browsers are not prefect! And Its give you the way to safe yourself when you need it.
When security risk found out, they will just post in their home page
Please disable javascript until its fixed
Like this, (I dont have offical page right now, so googled from somewhere)
http://browsers.about.com/b/2009/07/16/firefox-3-5-users-should-take-action-immediately.htm
However, until a fix is released, I
recommend that you either disable
JavaScript completely or use another
browser.

There are a few rare instances where JavaScript can be dangerous (but so can anything, including the massively ubiquitous Flash). The reason users actually do disable it or use addons like NoScript is largely unjustified paranoia.
In the end, users don't stick with behavior that breaks the websites they want to experience. So, I wouldn't expect JavaScript paranoia to be a long-term issue as only more and more sites depend on it (like this one).
It's similar to the hype we saw around cookies several years ago.

It can crash the browser, or do annoying things to users.
However, now a days Javascript has become such an integrated part of the internet (Gmail, bill paying for many companies sites, ect) that if you did disable it then browsing could arguably be difficult for you unless you had exceptions.

JavaScript has some very "odd" language features, like the handling of missing semicolons at statement endings by just ignoring the parse error ("semicolon insertion") or the behaviour of the typeof operator (array is an object).
You really need to know the language to know which things you should do and which are bad.
But there are also really good points about the language, like that it fully supports functional programming.

It is bad only you visit questionable sites. Without javascript you won't have apps like gmail, yahoo finance, etc.

Why is JavaScript allowed to be disabled in the browser?
Perhaps because computers are tools that serve humans? Computers speaking to computers via a protocol can mandate specific behaviour. Developers writing software for users have no such luxury.
It would be pointless for browser vendors to mandate that JavaScript "must" be enabled, since there are plenty of people who can't or don't want it. Especially since 90% of the time it's just being used by some spotty hipster to animate a cat picture.