https://github.com/mobxjs/mobx/blob/master/src/types/observablearray.ts#L506

export?function?isObservableArray(thing):?thing?is?IObservableArray<any>?{????
return?isObject(thing)?&&?isObservableArrayAdministration(thing[$mobx])????
}

const?isObservableArrayAdministration?=?createInstanceofPredicate(????
"ObservableArrayAdministration",????
ObservableArrayAdministration????
)

export?function?createInstanceofPredicate<T>(????
name:?string,????
clazz:?new?(...args:?any[])?=>?T????
):?(x:?any)?=>?x?is?T?{????
const?propName?=?"isMobX"?+?name????
clazz.prototype[propName]?=?true????
return?function(x)?{????
return?isObject(x)?&&?x[propName]?===?true????
}?as?any????
}