V8, JSC, etc have an interpreter (or JIT, or what have you), but they also include everything else: the GC, the standard library, the standard and core objects.

V8, JSC, etc have an interpreter (or JIT, or what have you), but they also include everything else: the GC, the standard library, the standard and core objects. e.g. the full runtime. Adding a couple of functions to an existing runtime is not rolling your own runtime.