Object properties defined as Symbols (even through classes) are still accessible by e.g. Object.getOwnPropertyDescriptors(myObject) Before the private fields,

Object properties defined as Symbols (even through classes) are still accessible by e.g. Object.getOwnPropertyDescriptors(myObject) Before the private fields, it was possible to create private properties through a WeakMap object which is somewhat clumsy and not very performant.