MediaStreamTrack.getCapabilities() - Web APIs
the getcapabilities() method of the mediastreamtrack interface returns a mediatrackcapabilities object which specifies the values or range of values which each constrainable property, based upon the platform and user agent.
... syntax const capabilities = track.getcapabilities() return value a mediatrackcapabilities object which specifies the value or range of values which are supported for each of the user agent's supported constrainable properties.

Index - Web APIs
2464 mediastreamtrack.getcapabilities() api, media capture and streams api, media streams api, mediastreamtrack, method, reference, getcapabilities the getcapabilities() method of the mediastreamtrack interface returns a mediatrackcapabilities object which specifies the values or range of values which each constrainable property, based upon the platform and user agent.

Capabilities, constraints, and settings - Web APIs
this function returns a mediatrackcapabilities object which lists each constrainable property supported by the browser and a value or range of values which are supported for each one of those properties.