Add a keyboard event listener to the element (focus or focusin) which will trigger the same functionality as the mouse event.
Engine scans for elements using one of the following events: mouseover or mousemove, but having no corresponding keyboard event (focus or focusin).
Using both keyboard-specific and mouse-specific events together ensures that content can be operated by a wide range of devices. For example, a script may perform the same action when a keyboard focus is detected that is performed when the mouse moves over an element.
<a href="menu.php" onmouseover="swapImageOn('menu')" onfocus="swapImageOn('menu')"