DEV 2.3 Use JavaScript wisely

Recommendations

• Do not rely on JavaScript alone for important content or functionality:
  • Ensure the content still makes sense and can still be used when scripts are turned off:
    • Provide alternative content using the <noscript> tag.
• JavaScript - enabled content that requires use of the mouse must be accessible without the mouse:
  • Use redundant event handlers:
    • OnKeypress + OnClick,
    • OnMousedown + OnKeydown,
    • OnMouseUP + OnKeyup,
    • Do not use OnDblclick.
• Do not rely solely on client-side scripts for form validation etc:
  • Use redundant server-side scripts as well as client side scripts
  • NB: This is also a good idea for security reasons.
• Avoid use of JavaScript links:
  • Unless you provide a default link that is not JavaScript dependent.
• Avoid automatic submission in form elements:
  • OnChange is often used for automatically submitting dropdown (select) menus. This is not accessible by the keyboard so a submit button should be provided.

Tip: Simple image rollover effects etc. are fine as long as the image replacement doesn't contain additional information.

Examples

Device independent event handlers
OnFocus, OnBlur, OnSelect would be the preferred way to detect events. Unfortunately, current browser support is patchy at best.