Output all properties of object

I noticed that the auto-completion tab in IDE is able to output more fields than a call to eg.:
Object.getOwnPropertyNames(Bangle)
Object.getOwnPropertyNames(Bangle.__proto__)

Specifically, some object-like fields:
Bangle.on
Bangle.removeListener etc

Similarly for a Promise object, I do not see the .then function as child object. How can I get full listing via javascript?

The auto-complete is able to show all of these fields from a promise instance:

>p.
constructor         apply
bind                call
replaceWith         catch
then                clone
emit                hasOwnProperty
length              on
removeAllListeners  removeListener
toString            valueOf

How do I get these items into a javascript list?

There isn't a specific function available to JS (it's calling jswrap_object_keys_or_property_names_cb(object, JSWOKPF_INCLUDE_NON_ENUMERABLE|JSWOKPF_INCLUDE_PROTOTYPE|JSWOKPF_NO_INCLUDE_ARRAYBUFFER)

But as I understand it you should be able to use Object.getOwnPropertyNames and then recursing down __prot­o__ of each object

I did try that recursion, I couldn't seem to get much results.