Ian Hickson wrote:
On Fri, 13 Feb 2009, Boris Zbarsky wrote:
The current Gecko behavior is that any stylesheet load started by parsing a
<style> or <link> tag will increment a counter on the document (well, on a
per-document script loader object, to be more precise). Completion of the load
will decrement the counter. While the counter is nonzero, <script> execution
is blocked. When it goes back to 0, the first pending script (if any) is run.
If this increments the counter again, no more scripts are run until the count
goes to 0 again.
So it doesn't matter how the script is created/inserted, but the only
stylesheets that block scripts are ones that the parser knows about. So only
the ones present in the original source or added via document.write. If you
createElement a <link> and insert it into the DOM, it won't block script
execution. Also, <link> elements pointing to alternate style sheets don't
block script execution.
So in this:
<!DOCTYPE html>
...
<script>
document.write('<link rel=stylesheet href=style>');
document.write('<script>a();<\/script>');
b();
</script>
...is the script paused after the second document.write() call, before a()
and b() execute?
No. What's paused is execution of new scripts, not of existing ones.
So in this case, b() executes immediately, while a() executes after the
stylesheet loads.
Here's a simple testcase to demonstrate that:
<!DOCTYPE html>
<script>
var res = "";
document.write('<link rel=stylesheet href="data:text/css,">');
document.write('<script>res+="a"<\/script>');
res+="b";
</script>
<body onload="alert(res)"></body>
I realize that this does mean that the execution order of a() and b() is
different if the <link> is written out as above....
-Boris
