I've recently been reading up on Javascript memory management, and decided to profile a portion of this app that I wrote recently. It makes a jQuery AJAX call every 5 seconds to another PHP page, essentially monitoring the database for changes. No DOM changes occured at any point.
Anyway, I ran the Profiler as well the Timeline thing on Chrome's devtools, and I'm not too sure how to interpret if I have a possible memory leak:
Timeline:
I didn't trigger manual garbage collection (via the button in the toolbar) at any point: 
Heap Allocation Profiler:
Ran this for a shorter amount of time, the portion between the 5.0 sec mark to 1.2 min mark doesn't have anything in the "Constructor" panel: 
If I'm not wrong, the drop in the first image (near the 240000ms mark) is a garbage collection event triggered by the browser.
My question is, why is it that in the second image I do not have any objects in the time that has elapsed (from the 5.0s to 1.2m mark), whilst the JS heap size continues to grow every 5 seconds?
I guess this doesn't indicate a memory leak, but is it true that the heap size continues to grow because I have effectively dereferenced the variables and objects in memory, but my script continues to create new variables every 5 seconds, and all of the dereferenced stuff only gets garbage collected after a few minutes?
More importantly, is this the proper way of handling memory usage? Meaning, is it sufficient to properly dereference your temporary variables, or would I also have to think about triggering garbage collection on my own as well?
P.S. The last question may come across as too broad, I am merely looking for best practices on this topic, as an add-on to the main question, which is to confirm my conclusion to why the heap size continues to grow is correct, as above.
