VI. How To?
6.4. Page Design
6.4.2. JavaScript
As seen in the Section 6.2. Accessibility Implementation Approach, the use of JavaScript can be problematic in terms of accessibility. Indeed if implemented without taking into account browser that do not support JavaScript or deactivate it, a JavaScript script can make a whole website inaccessible. The major accessibility problem due to JavaScript encountered on the Internet is the presence of drop-down menu where the dropping-down is generated by JavaScript; if no alternative, either implemented with a graceful degradation or a progressive enhancement approach, is offered, the menu is simply not usable, which means that users will not be able to navigate through the website via the menu. An example of such a menu can be seen on the website Alsacreations, which warns their visitors, that this menu may not be accessible to some users: http://css.alsacreations.com/xmedia/exemples/deroulant/menu-vertical.htm.
Another problem with the use of JavaScript is that it is often used to animate objects, whether this object is the whole page (for example: falling leaves one the screen) or a element of a menu (for example: a submenu appearing only when the mouse is over the element); this can be disturbing to people with learning disabilities and can make their browsing of the website difficult.
Several website treating about web accessibility consider that JavaScript should not be use on the Internet. I do not agree with this. JavaScript can also be a helping tool, and more especially can bring graphic enhancement to a web page. It would be a waste not to use a tool that allows the web developer to indicate, before a form is sent, where there are mistakes in the information specified by the user. JavaScript must not be forbidden, but it must be used with care.