How to Add Static Members in EcmaScript 5
ecmascript-5, javascript
Solution
You can't.
My class definition looks as follows `var Account = {};`
That's not a class (if we would call the classical model like that), but just a prototoype object. And as you only have that, you will need to use other variables for static members like an instances-cache or a create function:
var Account = {...};
var instances = [];
function createAccount(){...}
You could namespace them, of course:
var Account = {
proto: {...},
instances: [],
instantiate: function create(){...}
};
...but that looks very close to the classical pattern, doesn't it? The only difference would be that you had a `create` function on a namespace object instead of a constructor function as the namespace object.
You might also be interested in the question Object.create Prototype Chains, where I have discussed a full inheritance model working like that, with `create` and `inherit` methods that all "class objects" inherit from a `base`.
Further answer on your question in the comments:
Doesn't Object.create make the new operator obsolete in EcmaScript 5?
No. The `new` keyword does two things: Set up the prototype chain of the new instance, and apply the the constructor function. `Object.create` does only the first thing, so you can use it when you dont need a function (or dont want it to execute).
In your case, you have such a function, so the classical model wouldn't be wrong here as well. See also Using "Object.create" instead of "new".
Problem
I want to add a static function to a class in EcmaScript 5 JavaScript. My class definition looks as follows: ``` var Account = {}; Object.defineProperty(Account, 'id', { value : null }); ``` And I would create a new instance like this: ``` var theAccount = Object.create(Account); theAccount.id = 123456; ``` Now I want to add a static function to the `Account` class. If I had created the `Account` class using a constructor function and the `prototype` property like this: ``` var Account = function () { this.id = null; }; ``` ...I could just do: ``` Account.instances = {}; Account.createInstance = function () { var account = new Account(); account.id = uuid.v4(); Account.instances[account.id] = account; return account; }; ``` But since I am using `Object.defineProperty` and not the `prototype` property to add members, `Account.instances` and `Account.createInstance` would also be instantiated when calling `Object.create` and therefore be properties of the instance. How do i add a static member to a class when using EcmaScript 5 style object creation?