"use strict"; var _obj; const Base = { test: 1 }; const obj = _obj = { test: 2, set() { return babelHelpers.set(babelHelpers.getPrototypeOf(_obj), "test", 3, this, true); } }; Object.setPrototypeOf(obj, Base); expect(obj.set()).toBe(3); expect(Base.test).toBe(3); expect(obj.test).toBe(2);