Question

Assume the following program:

var SomeConstructor = function() { };
var instance = new SomeConstructor ();

The expression instance instanceof SomeConstructor yields True, so instance has to know somehow that it was constructed by the function SomeConstructor . Is there way to retrieve the name SomeConstructor directly from instance ?

(In my problem at hand, I have a hierarchy of prototypes implementing possible signals in my application. I have to access the type of a signal which shall be equivalent to the constructor used to create that signal.)

Answer 1

On Chrome (7.0.544.0 dev), if I do:

function SomeConstructor() { }

var instance = new SomeConstructor();

console.log(instance.constructor.name);

it prints ‘SomeConstructor’…but if SomeConstructor is defined as an unnamed function as you have it, it will print an empty string instead.

If I print instance.constructor it prints the same thing as it does if I print SomeConstructor in the code you have. The instanceof operator need only compare these two values to see that they are equal to be able to return true.