16 янв. 2012 г. · This is a syntax error. Operators such as != are a single operator, as opposed to a NOT applied to an EQUALS. There is no such operator as !

23 янв. 2009 г. · Strings and numbers are primitive values, not objects and therefore don't have a [[Prototype]], so it'll only work if you wrap them in regular objects.

6 апр. 2020 г. · A number primitive isn't instanceof anything because it isn't an object, and only objects are "instances" of something.

30 янв. 2020 г. · The reason instanceof String doesn't work, is because your literal string is not an instance of this class. Generally you'll want to avoid new String().

30 янв. 2012 г. · You could use the Class.isInstance method: if(!String.class.isInstance(str)) { /* do Something */ } but it is still negated and pretty ugly.

16 июл. 2020 г. · You could create a function that traverses the prototype chain and returns a list of all the super classes of an object including the class ...

15 окт. 2008 г. · I use: function isString(s) { return typeof(s) === 'string' || s instanceof String; } Because in JavaScript strings can be literals or objects.

31 янв. 2022 г. · A subclass will always be an instanceof itself and any of its parent classes. However, the reverse is not true: a parent class is not an ...

26 мая 2015 г. · In JS it doesn't seem possible to check if an argument passed to a function is actually of the type 'error' or an instance of Error.

30 авг. 2017 г. · The instanceof operator tests to see if the prototype property of a constructor appears anywhere in the prototype chain of an object.