css transitions on new elements
requestAnimationFrame()
(https://developer.mozilla.org/en-US/docs/Web/API/window.requestAnimationFrame) appears to work across Firefox, Chrome and Safari. A more reliable, logical solution that setTimeout()
. For older browsers (IE8), it will require a Polyfill (naturally, the transition won't occur, but the CSS will still change).
In Firefox, it does appear to be a race between layout completing and the CSS transition. Chrome is much more predictable. If I set the class name on a setTimeout()
, Chrome always works, Firefox only works if the setTimeout()
time is long.
With this code in Firefox (even using the setTimeout()
), the text shows immediately:
function f() {
var a = document.createElement('a');
a.id = 'id';
a.innerHTML = ' fading in?';
document.getElementsByTagName('p')[0].appendChild(a);
// at this point I expect the span element to be with opacity=0
setTimeout(function() {
a.className = 'fadeIn';
}, 10);
return false;
}
But, if I force a reflow by requesting a property that can only be returned after layout, it then starts to work in Firefox:
function f() {
var a = document.createElement('a');
a.id = 'id';
a.innerHTML = ' fading in?';
document.getElementsByTagName('p')[0].appendChild(a);
// at this point I expect the span element to be with opacity=0
// request property that requires layout to force a layout
var x = a.clientHeight;
setTimeout(function() {
a.className = 'fadeIn';
}, 10);
return false;
}
Furthermore, once I've request that property to force a layout, I can even remove the setTimeout()
and the animation works in Firefox.
function f() {
var a = document.createElement('a');
a.id = 'id';
a.innerHTML = ' fading in?';
document.getElementsByTagName('p')[0].appendChild(a);
// at this point I expect the span element to be with opacity=0
// request property that requires layout to force a layout
var x = a.clientHeight;
a.className = 'fadeIn';
return false;
}
You can see this last one work here in both Chrome and Firefox: http://jsfiddle.net/jfriend00/phTdt/
And, here's an article that discusses the phenomenon: http://gent.ilcore.com/2011/03/how-not-to-trigger-layout-in-webkit.html
I found a nicer way to trigger layout and make transitions work just after appending the element to the DOM:
window.getComputedStyle(element).opacity;