Advantages and Disadvantages of JavaScript

JavaScript is the most popular scripting language that is used in the client-side script programming on the Web. A lot of kinds of modern Web browsers have support of it. And many Websites nowadays contain features that are based on JavaScript. JavaScript can make dynamic updates to a HTML document in a browser and therefore can facilitate complex interactions between users and browsers or even servers.
JavaScript has some advantages and disadvantages. One advantage is that it runs fast since it is a client-side language. The code can be run immediately in the browser instead of having to contact the server and wait for an answer [1].
There are also disadvantages. One important disadvantage is that not all browsers can recognize JavaScript [2]. Using JavaScript limits the accessibility of a Website since old browsers, some mobile devices or screen readers do not recognize JavaScript. Besides, some users turn off the JavaScript support in their browsers for security reasons. It is reported that about 3% to 10% Web users turn off JavaScript support [3]. Another problem is that different browsers read JavaScript programs differently. It is suggested that the only way of being absolutely sure that a page will work on different browsers is to test it as widely as possible [4].

[1] http://www.mediacollege.com/internet/javascript/pros-cons.html
[2] http://zonorus.marlboro.edu/~lcarilli/designll/dis.htm
[3] http://www.killersites.com/mvnforum/mvnforum/viewthread?thread=2058
[4] http://www.wdvl.com/Authoring/JavaScript/PracticalJS/practicaljs1_3.html