Is there a technique for finding JsVar memory leaks?

Is there a technique that others use to diagnose such leaks?

Well, if you compile for Linux and make a test case in tests/foo.js then when you run the test, afterwards it'll shut down everything and will show you any variables that are left over.

Potentially you could do that exact same thing on ESP8266 if you want - just adding a few new lines in jsinteractive.c that copied what was done for save and then called jsvShowAllocated instead of save would probably do what you want.

Generally it's pretty obvious where they were created from what they are... For instance if you've got a bunch of ACCESS_POINT_SSID1, ACCESS_POINT_SSID2, etc then you can probably narrow it down to 1 line in scanAPs.