Check private methods in object preview. Running test: testPrivateMethods expression: new class extends class { constructor() { return new Proxy({}, {}); } } { #method() { return 1; } } [ ] expression: new class { #method() { return 1; } get #accessor() { } set #accessor(val) { } } [ [0] : { name : #accessor type : accessor } ] expression: new class extends class { #method() { return 1; } } { get #accessor() { } set #accessor(val) { } } [ [0] : { name : #accessor type : accessor } ]