Question

I would like to be able to read the value of a CSS property in the middle of a transition before it is fully executed. Is that possible? So if during a transition from 0% to 100%, I were to check halfway through, could I see it at 50%?

Answer 1

Is it possible to get the current css property during a transition in JavaScript?

Yes

var timer;

function test(e) {
    var $this;
    $this = $(this);
    timer = setInterval(function () {
        console.log($this.height());
    }, 500);
}
function untest(e) {
    clearInterval(timer);
}

$('div').mouseenter(test).mouseleave(untest);

div
{
    transition: height 10s;
    -moz-transition: height 10s;
    -webkit-transition: height 10s;
    width: 100px;
    height: 100px;
    background-color: #00F;
}

div:hover
{
    height: 300px;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div></div>

So far I’ve only tested firefox & chrome, but it appears that you can get the current CSS height via JS.

I can’t think of a reason why the browser wouldn’t report the change in styles to the DOM during a CSS transition.