There is an if (propp) under the js::LookupName function in \js\mozjs\mozjs\js\src\jsobj.cpp in spidermonkey under mozjs-52.9.1 version. How to judge if (propp) statement is true or false? Because in this function propp is of MutableHandleShape class instead of boolean.
hello @Jim_Ryna
check this link https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean
it show which value considered false
hope it help and have a nice day