JavaScript constructors (even when invoked with "new") can return values of unrelated classes.

demo.js

/*
 * Demo: a JavaScript constructor function, even when invoked with "new", can
 * return a completely different object, even one from a completely different
 * class.
 */

var counter = 0;
var lastMyClass;

function MyClass()
{
	this.myc_value = counter++;
	lastMyClass = this;
	console.error('constructed MyClass with value ', this.myc_value);
}

function MyOtherThing(wat)
{
	if (wat) {
		return (lastMyClass);
	}
}

/* Construct MyClass: value = 0 */
console.error(new MyClass());

/* Construct MyClass: value = 1 */
console.error(new MyClass());

/* Construct new MyOtherThing */
console.error(new MyOtherThing(false));

/*
 * Use constructor for MyOtherThing to return an instance of MyClass (!)
 */
var x = new MyOtherThing(true);
console.error('new MyOtherThing(true): properties: ', x);
console.error('new MyOtherThing(true): instanceof MyClass: ',
    x instanceof MyClass);
console.error('new MyOtherThing(true): instanceof MyOtherThing: ',
    x instanceof MyOtherThing);

output.txt

constructed MyClass with value  0
{ myc_value: 0 }
constructed MyClass with value  1
{ myc_value: 1 }
{}
new MyOtherThing(true): properties:  { myc_value: 1 }
new MyOtherThing(true): instanceof MyClass:  true
new MyOtherThing(true): instanceof MyOtherThing:  false