The required object is the name of an object or function.

The constructor property is a member of the prototype of every object that has a prototype. This includes all intrinsic JScript objects except the Global and Math objects. The constructor property contains a reference to the function that constructs instances of that particular object. For example:

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x = new String("Hi"); if (x.constructor == String) // Do something (the condition will be true).

or

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function MyFunc { // Body of function. } y = new MyFunc; if (y.constructor == MyFunc) // Do something (the condition will be true).

Version 2

Applies To: Array Object (JScript 5.6)| Boolean Object (JScript 5.6)| Date Object (JScript 5.6)| Function Object (JScript 5.6)| Math Object (JScript 5.6)| Number Object (JScript 5.6)| Object Object (JScript 5.6)| String Object (JScript 5.6)

Reference