I have it working in only JavaScript. Firefox won't let you update the keyCode, so all you can do is trap keyCode 13 and force it to focus on the next element by tabIndex as if keyCode 9 was pressed. The tricky part is finding the next tabIndex. I have tested this only on IE8-IE10 and Firefox and it works:

function ModifyEnterKeyPressAsTab(event) { var caller; var key; if (window.event) { caller = window.event.srcElement; //Get the event caller in IE. key = window.event.keyCode; //Get the keycode in IE. } else { caller = event.target; //Get the event caller in Firefox. key = event.which; //Get the keycode in Firefox. } if (key == 13) //Enter key was pressed. { cTab = caller.tabIndex; //caller tabIndex. maxTab = 0; //highest tabIndex (start at 0 to change) minTab = cTab; //lowest tabIndex (this may change, but start at caller) allById = document.getElementsByTagName("input"); //Get input elements. allByIndex = []; //Storage for elements by index. c = 0; //index of the caller in allByIndex (start at 0 to change) i = 0; //generic indexer for allByIndex; for (id in allById) //Loop through all the input elements by id. { allByIndex[i] = allById[id]; //Set allByIndex. tab = allByIndex[i].tabIndex; if (caller == allByIndex[i]) c = i; //Get the index of the caller. if (tab > maxTab) maxTab = tab; //Get the highest tabIndex on the page. if (tab < minTab && tab >= 0) minTab = tab; //Get the lowest positive tabIndex on the page. i++; } //Loop through tab indexes from caller to highest. for (tab = cTab; tab <= maxTab; tab++) { //Look for this tabIndex from the caller to the end of page. for (i = c + 1; i < allByIndex.length; i++) { if (allByIndex[i].tabIndex == tab) { allByIndex[i].focus(); //Move to that element and stop. return; } } //Look for the next tabIndex from the start of page to the caller. for (i = 0; i < c; i++) { if (allByIndex[i].tabIndex == tab + 1) { allByIndex[i].focus(); //Move to that element and stop. return; } } //Continue searching from the caller for the next tabIndex. } //The caller was the last element with the highest tabIndex, //so find the first element with the lowest tabIndex. for (i = 0; i < allByIndex.length; i++) { if (allByIndex[i].tabIndex == minTab) { allByIndex[i].focus(); //Move to that element and stop. return; } } } }

To use this code, add it to your html input tag:

<input id="SomeID" onkeydown="ModifyEnterKeyPressAsTab(event);" ... >

Or add it to an element in javascript:

document.getElementById("SomeID").onKeyDown = ModifyEnterKeyPressAsTab;

A couple other notes:

I only needed it to work on my input elements, but you could extend it to other document elements if you need to. For this, getElementsByClassName is very helpful, but that is a whole other topic.

A limitation is that it only tabs between the elements that you have added to your allById array. It does not tab around to the other things that your browser might, like toolbars and menus outside your html document. Perhaps this is a feature instead of a limitation. If you like, trap keyCode 9 and this behavior will work with the tab key too.