I wrote this a few+ years back...
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Javascript - To Support or Not to Support
Contemporary web-development is founded increasingly on the "Web 2.0" vision of rich, interactive media and dynamic interaction with background, server-side technologies. JavaScript provides an invaluable tool to enhance modern web pages and increase the sophistication of website interaction to rival and even surpass that of desktop applications.
The introduction of Ajax (Asynchronous JavaScript And XML) and its ability to provide new content and functionality to a website without the need to refresh the entire page has become the backbone of the "Web 2.0" revolution. So much so that the majority of rich and interactive websites rely on JavaScript and in particular Ajax.
There are very few good motives to disable JavaScript in light of modern browser capacities. Contemporary browsers permit the regulation of JavaScript to address security issues and can be tuned to suit the needs and concerns of any user without disabling JavaScript completely. The growing sophistication of anti-malware solutions coupled with the evolution of browsers allows JavaScript to be enabled safely for the vast majority of users.
Other media, such as Radio, Television and even Print, do not provide 100% coverage of all potential customers, and the same is true of the Internet. Admittedly, these other media do not steal identities and compromise one's computer to nefarious ends. However, most of the dangers of enabling JavaScript in a web browser can be ameliorated or entirely eliminated by relatively simple precautions.
The use of JavaScript is not an accessibility issue that discriminates against users with disabilities, nor does it affect visitors based on any preconceived geographic, social, cultural, or ethnic criteria. There is a small percentage of web users who make a conscious decision to disable JavaScript and as a result do not benefit from this significant advancement in web technology. Those who elect to disable the benefits of JavaScript miss out on a very rich tapestry of modern, dynamic interactions, which dramatically improve the quality of the "online experience."
It is possible to develop websites which maintain parallel content that does not rely on JavaScript; however, there are real costs to maintaining such a system. Server-side management can substitute dynamic behaviour to some extent, but there will be significant degradation of user experience and website performance. Such an approach cannot provide the same benefits or positive user experience as offered when JavaScript is available.
Any entity considering the publication of web pages should determine the degree of its reliance on JavaScript in terms of expected Return On Investment (ROI). Some questions by which to assess potential ROI are:
With the answers to these questions in hand, a rational decision can be reached.