Why [object Object] mentions "object" twice?

exebook提出了一个问题:Why [object Object] mentions “object” twice?,或许与您遇到的问题类似。


All objects have a toString method that displays something in the format [object type], where type is the object type.

When called on null you get [object Null] and when called on an object you get the string [object Object] because it's based on the Object constructor (capital "O"), that's why it says object twice, it's an object of the type Object.


JSON is a lightweight data-interchange format, and doesn't really have anything to do with JavaScript other than being named "JavaScript Object Notation" because it's written like a JavaScript object.