ECMAScript

[skaterdav85]

Does anyone understand the hierarchy of ECMAScript Reference and Primitive types? I noticed that Object.constructor returns Function, yet I read that all the reference and primitive types inherit from the Object reference type. If Object.constructor returns Function, but Function inherits from Object, isn't that like saying the top most object Object is dependent on it's child Function?

[justsomeguy]

Object is the base type. A function is a subclass of an object. A function is an object, but an object is not a function. The base object class does not inherit from a function, the base function class inherits from the base object.

[skaterdav85]

"A function is a subclass of an object." Don't you mean, Function is a subclass of Object? A function would be an instance of Function."The base object class does not inherit from a function"Then why does Object.constructor equal Function?

[Ingolme]

"A function is a subclass of an object." Don't you mean, Function is a subclass of Object? A function would be an instance of Function."The base object class does not inherit from a function"Then why does Object.constructor equal Function?

Because all constructors are functions. Constructor is the function that runs when an object is instantiated.

[skaterdav85]

so if Object is a constructor, and all constructors are functions, and functions are objects of Function, wouldnt that mean Object is an instance of Function?

[Ingolme]

An object is not a constructor. An object has a constructor. An object is an instance of Object.Object is an object. Object.constructor is a function. The constructor, not the object itself.

[justsomeguy]

Then why does Object.constructor equal Function?

It doesn't equal function, it is a function. The constructor is a function that gets executed when a new object gets created. The constructor does not create the actual object, it is optional code that runs after the object gets created to run whatever initialization code your object instance needs. I think you're conflating the constructor with the object, but they're not the same. The constructor is optional, if present it gets executed after the object gets created.

[skaterdav85]

ok so let me get this straight. there are reference and primitive types provided in ECMAScript. They are String, Number, Function, Boolean, and Object. Object is an object, Number is an object, etc, and their constructor property is a function (an instance of Function) that gets executed to run whatever initialization code the object instance needs. String, Number, Function, etc all inherit from Object.

[justsomeguy]

That sounds right.

[skaterdav85]

Actually, I take some of that back. The constructor property of String, Number, etc isn't a function that is an instance of Function. I think it is just the built in Function constructor function.

function Person (name) {  this.name = name;}var david = new Person ('david');david.constructor; // Person () function was used to initialize the david objectvar someObject = new Object ();someObject.constructor; // Object () function was used to initialize the someObject objectObject.constructor; //Function () function was used to initialize the Object object