instanceof

The instanceof operator tests to see if the prototype property of a constructor appears anywhere in the prototype chain of an object. The return value is a boolean value.

Interviewer: to write a fakeInstanceOf, you must meet the following test cases:

function fakeInstanceOf (instance, parent): Boolean {}

//=> true
fakeInstanceOf([], Array)

//=> true
fakeInstanceOf([], Object)

//=> true
fakeInstanceOf(x => x, Object)

//=> false
fakeInstanceOf('hello', Object)

The following is a reference

function fakeInstanceOf (instance, parent) {
 if (typeof(instance) !== 'object' && typeof(instance) !== 'function') {
 return false
 }
 let proto = instance?.__proto__ || null
 while (true) {
 if (proto === null) { return false }
 if (proto === parent.prototype) { return true }
 proto = proto.__proto__
 }
}