Some of the declarations here may look strange at first glance. Explanations for [some of?] these are found below.

You will note that the Object class us declared using Class Decomposition (which makes use of the construct signature) and appears incomplete. This is intentional: the declarations will merge with the base ECMAScript Object and ObjectConstructor types from the core es5 library. Where extra documentation existed for ExtendScript on pre-existing members (e.g. ObjectConstructor.prototype), the type declarations were included again. TypeScript merges the additional documentation, resulting in augmented documentation.

The $ object is currently implemented as a const object with functions grafted onto it via the Helper interface. This was done because while the $ object is identified as "[Helper Object]" in the ExtendScript Toolkit's Data Browser, there is no "Helper" class or type otherwise to be found.

There is no actual PremiereObject type in the Premiere Pro APIs. However, all Premiere Pro API object instances have additional class members that don't appear in the base ExtendScript Object class. This is a middleman type that allows auto-complete to resolve these members.