How do you clear the focus in javascript?

Question

Answer: document.activeElement

To do what you want, use document.activeElement.blur()

If you need to support Firefox 2, you can also use this:

function onElementFocused(e)
{
    if (e && e.target)
        document.activeElement = e.target == document ? null : e.target;
} 

if (document.addEventListener) 
    document.addEventListener("focus", onElementFocused, true);

.focus() and then .blur() something else arbitrary on your page. Since only one element can have the focus, it is transferred to that element and then removed.

document.activeElement.blur();

Works wrong on IE9 - it blurs the whole browser window if active element is document body. Better to check for this case:

if (document.activeElement != document.body) document.activeElement.blur();

None of the answers provided here are completely correct when using TypeScript, as you may not know the kind of element that is selected.

This would therefore be preferred:

if (document.activeElement instanceof HTMLElement)
    document.activeElement.blur();

I would furthermore discourage using the solution provided in the accepted answer, as the resulting blurring is not part of the official spec, and could break at any moment.

dummyElem.focus() where dummyElem is a hidden object (e.g. has negative zIndex)?

You can call window.focus();

but moving or losing the focus is bound to interfere with anyone using the tab key to get around the page.

you could listen for keycode 13, and forego the effect if the tab key is pressed.