Constructors Which Create Constructors (JavaScript)

Question

In a simulation I'm making, I'll have an Element class, which I'll call with params about the properties of that Element (melting and boiling temperatures, rules for reactions with other Elements, color, density, etc.) to create the basic types of Elements (water, oxygen, carbon, etc.). From these, I simply would like to create new "Atoms" from the water, oxygen, and carbon templates I would have. I'm wondering if there's a way to use a constructor (Element) to create a new constructor (like Water)? For example, I would like to be able to do something like this.

var Element = function(/* params */) {
    // common element properties and basic functions
}
var Water = new Element(); // create the new element
var WaterAtom = new Water(); // create the atom (an instance of the element)
// draw the atom, manipulate it, react with other atoms, etc.

I'm basically asking, can a constructor create another constructor? I would like it this way so I don't have to create tons and tons of .prototype code that extends the basic Element class.

What is this supposed to accomplish? Where do you specify new behavior for the Water class? — SimpleJ
– SimpleJ, Commented Feb 18, 2016 at 0:57
No, a constructor can't create another constructor, you should consider it to be a simple constructor-producing function that is not invoked with new. — Bergi
– Bergi, Commented Feb 18, 2016 at 1:11
Are these things supposed to be subclasses of Element? Then Element is a constructor that constructs element instances - not constructors. — Bergi
– Bergi, Commented Feb 18, 2016 at 1:12

Bergi · Accepted Answer · 2016-02-18 16:45:46Z

1

I think what you are looking for is

function Element(…) {
    // init properties that all elements share
}
Element.prototype.… = function(…) { … }; // add all methods of elements

Element.makeType = function(rules) {
    function ElementType(…) {
        Element.call(this, …);
    }
    ElementType.prototype = Object.create(Element.prototype);
    ElementType.prototype.constructor = ElementType;
    ElementType.prototype.rules = rules;
    return ElementType;
};

so that you can use it like

var Water = Element.makeType(function(…) {
    // do whatever makes water special
});

var drop = new Water(…);

answered Feb 18, 2016 at 16:45

Bergi

671k162 gold badges1k silver badges1.5k bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Drew Christensen Over a year ago

Nice! I'll try it out.

SimpleJ · Accepted Answer · 2016-02-18 16:50:06Z

1

You could just write a utility function for generating subclasses of Element:

function Element() {}

function subElement() {
  function SubElement() {}
  SubElement.prototype = Object.create(Element.prototype);
  return SubElement;
}

var Water = subElement();
var waterAtom = new Water();

edited Feb 18, 2016 at 16:50

answered Feb 18, 2016 at 1:00

SimpleJ

14.9k13 gold badges62 silver badges97 bronze badges

3 Comments

Bergi Over a year ago

Object.create(Element); - nope.

Drew Christensen Over a year ago

@SimpleJ Hmm... I'll try it.

SimpleJ Over a year ago

@Bergi Woops. I guess I've become too use to the class syntax

Collectives™ on Stack Overflow

Constructors Which Create Constructors (JavaScript)

2 Answers 2

1 Comment

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related