Access to a ES6 / ES7 static class variable within class and constructor

Question

I'm having a pretty strange problem:

class AddOrSelectAddress {
    static allCountries = {
        AD: "Andorra",
        AE: "Vereinigte Arabische Emirate",
        AF: "Afghanistan",
        // ...
    };

    constructor() {
        console.log('new');
        console.log(this.allCountries); // prints "undefined"
    }
}

const myInstance = new AddOrSelectAddress();

Why does that happen? I would expect, that the this.allCountries would contain the object there.

"Static methods are not directly accessible using the this keyword from non-static methods. You need to call them using the class name: CLASSNAME.STATIC_METHOD_NAME() or by calling the method as a property of the constructor: this.constructor.STATIC_METHOD_NAME()." (Source) - It's for methods but I would guess that this will also count for properties. — Andreas
– Andreas, Commented Nov 8, 2019 at 17:04

Mosè Raguzzini · Accepted Answer · 2019-11-08 17:06:58Z

2

Static methods and properties are accessible through classes, not through this keyword:

class AddOrSelectAddress {
    static allCountries = {
        AD: "Andorra",
        AE: "Vereinigte Arabische Emirate",
        AF: "Afghanistan",
        // ...
    };

    constructor() {
        console.log('new');
        console.log(AddOrSelectAddress.allCountries);
    }
}

const myInstance = new AddOrSelectAddress();

edited Nov 8, 2019 at 17:06

answered Nov 8, 2019 at 17:05

Mosè Raguzzini

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4 Comments

Barmar Over a year ago

Minor nit: it's a property, not a method (methods are properties that are functions).

André Reichelt Over a year ago

Thank you very much. This is the solution. Can I somehow make that static property private?

Mosè Raguzzini Over a year ago

@AndréReichelt static #allCountries = {...}; will be both static and private

André Reichelt Over a year ago

@MosèRaguzzini Thank you very much! pretty "special" syntax, though. Looks like JS wants to be extra fancy.

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