Lock tab key with javascript?

How to lock or disable and again the tab key with javascript?

$(document).keydown(function(objEvent) {
    if (objEvent.keyCode == 9) {  //tab pressed
        objEvent.preventDefault(); // stops its action
    }
})

You can do it like this:

$(":input, a").attr("tabindex", "-1");

That will disable getting focus with tab in all links and form elements.

Hope this helps

Expanding on Naftali aka Neal's answer, here's how you'd do it with vanilla JS and both start and stop Tab behavior buttons:

let stopTabFunction = function(e) {
  if (e.keyCode == 9) {
    e.preventDefault();
  }
};
document.getElementById('stopTabButton').onclick = function() {
  document.addEventListener('keydown', stopTabFunction);
};
document.getElementById('resumeTabButton').onclick = function() {
  document.removeEventListener('keydown', stopTabFunction);
};

<input type="text"/>
<input type="text"/>
<input type="text"/>
<input type="text"/>
<input type="text"/>
<input type="text"/>
<br/><br/>
<input type="button" id="stopTabButton" value="Stop Tab!"/>
<input type="button" id="resumeTabButton" value="Resume Tab!"/>

Note that this also works for Shift + Tab (reverse direction).

JSFiddle

However, in my case, I wanted slightly different behavior: I wanted to basically lock down Tab focus to a single div. To do this, I placed a div before and after it, gave them both tabindex="0" (document-defined tab order on the div's themselves), to make the outer edges of the div focusable, like so:

<div id="beforeMyDiv"></div>
<div id="myDiv">
  <!-- Only want Tab indexing to occur in here! -->
</div>
<div id="afterMyDiv"></div>

Then, I changed the function from earlier to this:

//Get the div's into variables etc.
//...

let forceTabFocusFunction = function (e) {
    if (e.keyCode == 9) {
        //Force focus onto the div.
        if (!myDiv.contains(document.activeElement)) {
            if (e.shiftKey) {
                afterMyDiv.focus();
            } else {
                beforeMyDiv.focus();
            }
        }
    }
};

That did the trick nicely.