Here on Stack Overflow, I would like to be able to use the tab key within the WMD editor text box to tab over 4 spaces. The way it is now, the tab key jumps my cursor down to the Tags.

Vote for this feature at UserVoice: http://stackoverflow.uservoice.com/pages/general/suggestions/15889

Is there some JavaScript that will capture the TAB key in the text box before it bubbles up to the UI?

I understand some browsers (i.e. FireFox) may not allow this. How about a custom key-combo like Shift-TAB, or Ctrl-Q?

                    <SCRIPT TYPE="text/javascript"><!--
function CatchTab(myfield,e) {
var keycode;
if (window.event) {
keycode = window.event.keyCode;
} else if (e) {
keycode = e.which;
} else {
return true;

if (keycode == 9) { // if is the tab key
// Do stuff, return false to prevent key from being output

<INPUT NAME="MyText" TYPE="Text" onKeyPress="return CatchTab(this,event)" />
Yaakov Ellis
+2  A: 

The previous answer is fine, but I'm one of those guys that's firmly against mixing behavior with presentation (putting JavaScript in my HTML) so I prefer to put my event handling logic in my JavaScript files. Additionally, not all browsers implement event (or e) the same way. You may want to do a check prior to running any logic:

document.onkeydown = TabExample;

function TabExample(evt) {

var evt = (evt) ? evt : ((event) ? event : null);
if(evt.keycode == 9) {

// do work


+15  A: 

I'd rather tab indentation not work than breaking tabbing between form items.

If you want to indent to put in code in the Markdown box, use Ctrl+K (or ⌘K on a Mac).

In terms of actually stopping the action, jQuery (which Stack Overflow uses) will stop an event from bubbling when you return false from an event callback. This makes life easier for working with multiple browsers.

Mike Tomasello
+3  A: 

I would advise against changing the default behaviour of a key. I do as much as possible without touching a mouse, so if you make my tab key not move to the next field on a form I will be very aggravated.

A shortcut key could be useful however, especially with large code blocks and nesting. Shift-TAB is a bad option because that normally takes me to the previous field on a form. Maybe a new button on the WMD editor to insert a code-TAB, with a shortcut key, would be possible?

Wally Lawless
+1  A: 

@Mike Tomasello

I like the Ctrl-K functionality because it takes me right to a "code" block, but once I'm inside the code block, I would like to easily tab-over, and Ctrl-K doesn't accomplish this.

+10  A: 

Even if you capture the keydown/keyup event, those are the only events that the tab key fires, you still need some way to prevent the default action, moving to the next item in the tab order, from occurring.

In Firefox you can call the "preventDefault()" method on the event object passed to your event handler. In IE, you have to return false from the event handle. The JQuery library provides a preventDefault method on it's event object that works in IE and FF.

<input type="text" id="myInput">
<script type="text/javascript">
    var myInput = document.getElementById("myInput");
    if(myInput.addEventListener ) {
    } else if(myInput.attachEvent ) {
        myInput.attachEvent('onkeydown',this.keyHandler); /* damn IE hack */

    function keyHandler(e) {
        var TABKEY = 9;
        if(e.keyCode == TABKEY) {
            this.value += "    ";
            if(e.preventDefault) {
            return false;
I just corrected line 4, from "if (el.attachEvent)" to "if (myInput.attachEvent)"

Don't forget to check for the focused window, and let it bubble up normally if you are not in the editor textarea.

+1  A: 

In Chrome on the Mac, alt-tab inserts a tab character into a <textarea> field.

Here’s one: . Wee!

Paul D. Waite

there is a problem in best answer given by ScottKoon

here is it

} else if(el.attachEvent ) { myInput.attachEvent('onkeydown',this.keyHandler); /* damn IE hack */ } Should be

} else if(myInput.attachEvent ) { myInput.attachEvent('onkeydown',this.keyHandler); /* damn IE hack */ }

Due to this it didn't work in IE. Hoping that ScottKoon will update code