How can I tell when changes to jquery html() have finished ?

Question

I'm using jQuery to change the HTML of a tag, and the new HTML can be a very long string.

$("#divToChange").html(newHTML);

I then want to select elements created in the new HTML, but if I put the code immediately following the above line it seems to create a race condition with a long string where the changes that html() is making may not necessarily be finished rendering. In that case, trying to select the new elements won't always work.

What I want to know is, is there an event fired or some other way of being notified when changes to html() have finished rendering ? I came across the jQuery watch plugin, which works alright as workaround but it's not ideal. Is there a better way ?

Answer 1

As a commenter already mentioned, JavaScript is single threaded, so you can't get race conditions.

What may trip you up however, is the fact that the UI will not update itself based on JavaScript, until a thread is finished. This means that the entire method must finish, including all code after you call html(...), before the browser will render the content.

If your code after calling html(...) relies on the layout of the page being recalculated before continuing, you can do something like this:

$("#divToChange").html(newHTML);
setTimeout(function() {
    // Insert code to be executed AFTER
    // the page renders the markup
    // added using html(...) here
}, 1);

Using setTimeout(...) with a time of 1 in JavaScript defers execution until after the current JavaScript code in the calling function finishes and the browser has updated the UI. This may solve your problem, though it is difficult to tell unless you can provide a reproducible example of the error you're getting.

Answer 2

Thanks for your help. In trying to get a reproducible example, I realised I was wrong in my original question about where the problem is. The newHTML includes code to load a very small .swf, and the subsequent Javascript is trying to interact with it. Although the HTML itself is being changed, the Flash file itself is not fully loaded in time. It does work if I added an alert() or a long loop straight after the call to html() though, which is why I thought it was acting like a race condition.

I still need a Javascript way of knowing when the Flash file is fully ready to interact with, but using the jQuery Watch plugin works ok for that.