Javascript empty loop

Question

I saw some code like this:

while(ajaxCallInProgress)
        {
        }
        ajaxCallInProgress = true;

What is the use of this empty loop in javascript? What its does ? Thanks in advance...

Answer 1

if ajaxCallInProgress is a truthy expression, this will be an infinity-loop (and therefore, will freeze the interpreter forever).

It makes sense in a lot of places to do something, while a specific condition is true, but in all of those cases, the condition which is checked must set to a falsy value at some point within the loop body.

Since ECMA-/Javascript doesn't support multiple threads (I Just ignore web-workers here), there is no way this variable could get modified somewhere else.

Conclusion:

whereever you saw this code you either didn't copy & paste it completely or the author of this code didn't really know what he is doing.

Answer 2

It loops endlessly until ajaxCallinProgress becomes false. While it loops it's eating as much CPU as one thread can.

I think this is a very bad example of performing a blocking operation, a better way to handle something that is asynchronous would be with events.

Hope this helped.