How to detect when cancel is clicked on file input?

Question

How can I detect when the user cancels a file input using an html file input?

onChange lets me detect when they choose a file, but I would also like to know when they cancel (close the file choose dialog without selecting anything).

Answer 1

While not a direct solution, and also bad in that it only (as far as I've tested) works with onfocus (requiring a pretty limiting event blocking) you can achieve it with the following:

document.body.onfocus = function(){ /*rock it*/ }

What's nice about this, is that you can attach/detach it in time with the file event, and it also seems to work fine with hidden inputs (a definite perk if you're using a visual workaround for the crappy default input type='file'). After that, you just need to figure out if the input value changed.

An example:

var godzilla = document.getElementById('godzilla')

godzilla.onclick = charge

function charge()
{
    document.body.onfocus = roar
    console.log('chargin')
}

function roar()
{
    if(godzilla.value.length) alert('ROAR! FILES!')
    else alert('*empty wheeze*')
    document.body.onfocus = null
    console.log('depleted')
}

See it in action: http://jsfiddle.net/Shiboe/yuK3r/6/

Sadly, it only seems to work on webkit browsers. Maybe someone else can figure out the firefox/IE solution