ARCHIVED - Defining the JavaScript issue for accessibility

4.1 Document.write

Screen-readers such as JAWS will not read text updated with document.write. Additionally, document.write will incorrectly update browsers such as Lynx. You have to find another way to design your site.

Groups affected: group 2 and group 3

4.2 Window.status

The status bar of certain browsers provides additional information to the client when the cursor is placed over a link. You can control the information that appears in the status bar by using window.status. Browsers such as Lynx will not read text updated or created using window.status. Additionally, if you update the status bar repeatedly, clients who use a screen-reader will find it difficult to navigate and the page may become unusable. Do not use the status bar to convey additional information. Instead, use the title attribute and make sure that links make sense when taken out of context.

Groups affected: group 2 and group 3

4.3 Cursor position

If you use a script that relies on the co-ordinates of the cursor, consider how clients using a keyboard will emulate this activity. If a keyboard can't be used to emulate an activity, find a different solution.

Groups affected: group 1, group 2, and group 3

4.4 JavaScript pseudo protocol links

You should avoid the JavaScript pseudo protocol because it is not considered accessible. Clients don't always enable JavaScript or their browser doesn't support it. Also, a number of JavaScript capable browsers do not support pseudo protocol. Screen-readers such as JAWS will not understand pseudo protocol links while browsers such as Lynx will update incorrectly. You have to find another way to design your site. Below is an example of a JavaScript pseudo protocol link.

<a href="javascript:window.open('fred.html',' windowname','height=100')">Fred</a>

Groups affected: group 2 and group 3

4.5 DoubleClick event handlers

Currently, device-independent or keyboard-equivalent event handlers are not available for the doubleClick event handler.

Groups affected: group 1, group 2, and group 3

4.6 Pop-up windows / automatic opened windows

There are other ways of conveying information than through pop-up windows. CLF standards strongly discourage pop-up windows because they are not considered accessible. If you have to use pop-up windows, you have to warn clients before a new browser window opens. You also have to inform clients when they are in a new browser window.

Groups affected: group 1, group 2, and group 3

4.7 Drag-and-drop features

Most clients with a disability can't use drag-and-drop features unless a similar keyboard-driven feature is provided.

Groups affected: group 1, group 2, and group 3

4.8 Tickers

Tickers are segments of scrolling text on the screen. They are often used to deliver stock quotes and weather information. Tickers have to be a feature that clients enable themselves as they can draw the focus away from the area of the site that clients are trying to read. This means that the client's focus will move repeatedly toward the scrolling text resulting in the site being impossible to use.

Groups affected: group 1, group 2, and group 3

4.9 Auto refresh feature

Set the auto refresh feature so that clients have to enable it themselves as it can draw the focus away from the area of the site that clients are trying to read. This means that the client's focus will move repeatedly toward the scrolling text resulting in the site being impossible to use.

Groups affected: group 1, group 2, and group 3

4.10 Forms without submit buttons

JavaScript is often used to update or to submit information. The onChange event handler is frequently used in select boxes for calendar-type pages. As they are not considered accessible, do not use the onChange and onSelect event handlers in select/combo boxes.

Groups affected: group 1, group 2, and group 3

4.11 Links created with JavaScript or pointing to a JavaScript function

Most screen-readers are unable to handle links created with JavaScript or that point to JavaScript functions. Also, clients with browsers that do not support JavaScript or with JavaScript disabled can't use these types of links. Avoid using links created with JavaScript or links pointing to JavaScript functions.

Groups affected: group 1, group 2, and group 3

4.12 Event handlers

JavaScript is often used to process events on a Web page. Event handlers must be entirely mouse-independent. Use device-independent event handlers or pair mouse-based event handlers with keyboard-based ones. The functions that use these event handlers must not impede or obstruct client navigation.

The most common error involving event handlers is using submit buttons that call JavaScript functions to validate and/or submit data. JavaScript event handlers will function incorrectly with older browsers, older assistive technologies, text-only browsers such as Lynx, or browsers with JavaScript disabled.

Groups affected: group 1, group 2, and group 3

4.13 Error Messages

Pop-up windows are extremely disorienting for clients who use a screen-reader. Clients with a visual impairment may not receive an error message for a form if the error message is on a separate page (pop-up window) as the screen-reader will not read it. If the error message is on a separate page, clients are unable to receive the additional information provided on that page as they are often locked into a field.

Additionally, when clients finish reading a pop-up window, the focus will be returned to the beginning of the original page. This means that clients have to navigate through the entire page to find where the error is occurring. It is better to re-display the form with the error message embedded as it is more convenient for all clients.

If you have client-side form validation (using JavaScript or other methods), you also need to have server-side form validation installed for clients who have problems with scripting, who don't have scripting support, or who have disabled scripting.

Groups affected: group 1, group 2, and group 3