4.2 Constructor Functions

>>>

function MyObject() {}

>>>

MyObject()

undefined

Object constructor functions are normal functions...

>>>

new MyObject()

{}

...called using the new keyword. This creates a new empty object instance initialized by the constructor function.

>>>

var obj = new MyObject()

The object instance is created before the function executes. And is returned as a default return value.

>>>

obj instanceof MyObject

true

The new object is instanceof the constructor function, in this case MyObject.

>>>

obj.constructor

function MyObject() {}

The non-enumerable constructor property provides a back-reference to the constructor function.

>>>

obj.constructor === MyObject

true

With the constructor property, it is possible to build an alternative instanceof implementation (but not recommended).

>>>

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