Hi all,
I have some question on the behavior of javascript function alert() in
the firefox browser. I don't if I am posting to the right forum.
Please tell me if I should post it anywhere else.
So here is the problem:
Everyone is talking about that there is only a single thread for
interpreting the javascript code for each page. That means you should
not be able to create interleaving behavior, for example for two piece
of code attached to two different event handler.
However, you can some how create interleaving behavior by "alert()",
here is the example: Suppose we defined a function Callpage() which
use XMLHttpRequest to request another page asynchronously. on the
request return, It will execute the callback registered in
"onreadystatechange".
Now we execute in onclick event of some button the following code:
Callpage();
alert("abc");
alert("def");
A wired behavior can be observed in the Firefox is that, when "abc"
pops up, if we do not click OK, wait for Callpage's request return,
then the callback will be executed immediately, without waiting the
current piece of code being finished. that is
alert("abc")->callback execution->alert("def")
Actually you can observe different behavior in different browser, for
example in Google Chrome, you can only observe:
alert("abc")->alert("def")->callback execution
So the questions are:
What do alert do in Firefox? My intuition is that alert() will pack
the current continuation, and add a event for clicking the OK buttion,
and when it returns, it will execute the continuation. Then the single
thread story is still not broken. However, since call-with-
continuation is not native in SpiderMonkey, it still bothers me how
it is actually implemented.
Thanks for reading, your comments are welcome.
Zhengqin
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