Typescript 3.8.3 : Sharp notation for private method must be alloweded

[Binau]

Search Terms

TS18022, sharp

Suggestion

Sharp notation for private method must be alloweded : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes/Class_fields#Private_instance_methods

Use Cases

class Test {
#test() {}
}

Examples

class Test {
#test() {}
}
=> TS18022: A method cannot be named with a private identifier.

Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

[orta]

It is supported: https://www.typescriptlang.org/play/?ts=3.8.0-beta&e=70#example/private-class-fields

[Binau]

i think their is not private method in your example. try to write #greet() to replace greet() method in your example, and you have this error message : "A method cannot be named with a private identifier.(18022)".

[orta]

True yeah, and I can't seem to find another issue about this 👍

[Jamesernator]

The relevant proposal for private methods is here: https://github.com/tc39/proposal-private-methods

Private methods are only shipping in XS so far, but they are in active development in V8.

[Binau]

In the same way, static private attribute in class must be allowed too.
however :

class Test {
static #TEST:any;
}

do :

TS18019: 'static' modifier cannot be used with a private identifier

Référence : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes/Class_fields#Private_fields
proposal : https://github.com/tc39/proposal-static-class-features
Already compatible in edge (79), node (13), chrome

[davidbayo10]

In the same way, static private attribute in class must be allowed too.
however :

class Test {
static #TEST:any;
}

do :

TS18019: 'static' modifier cannot be used with a private identifier

Référence : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes/Class_fields#Private_fields
proposal : https://github.com/tc39/proposal-static-class-features
Already compatible in edge (79), node (13), chrome

This is a problem...

class S {

  static #instance: S;

  static getInstance(): S {
    if (!this.#instance) {
      this.#instance = new S();
    }

    return this.#instance;
  }

}

How can I perform this?

Thank you a lot in advance

[mellonis]

In the same way, static private attribute in class must be allowed too.
however :

class Test {
static #TEST:any;
}

do :

TS18019: 'static' modifier cannot be used with a private identifier

Référence : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes/Class_fields#Private_fields
proposal : https://github.com/tc39/proposal-static-class-features
Already compatible in edge (79), node (13), chrome

This is a problem...

class S {

  static #instance: S;

  static getInstance(): S {
    if (!this.#instance) {
      this.#instance = new S();
    }

    return this.#instance;
  }

}

How can I perform this?

Thank you a lot in advance

Private properties and methods should not be accessible from outside the class instance.
Own methods of a class should have access to private methods of a class if they are static or not.

Can be a constructor private? If it's not, is this singleton example valid?

[davidbayo10]

#instance is a private and static field inside S class and getInstance is static too. As you can create this kind of static fields and methods in NodeJS, it should work in TS

https://node.green/#ESNEXT-candidate--stage-3--static-class-fields-private-static-class-fields

Node allow this way for creating singleton patterns. Try out yourself. I don't understand why TS is showing that error.

[mellonis]

It was a misunderstanding. I thought that your problem was the 'inaccessibility' of the private field #instance from the not private method getInstance(). I agree that there should be no problem.

Anyway. That's the point to use this pattern? Anyone can instantiate this class with new operator. How can I prevent this or it should be a convention in a team not to use new operator with this class?

[davidbayo10]

That's a good point. I think we can use a private constructor. I think It fits well with this pattern. But, in a singleton pattern everyone can use getInstance method or new. If getInstance method exists, then should be used

[mellonis]

I'm also unable to use private getters and setters in a class in TS.

class GSExample {
    #a: number = 0;

    get a() { // this is file
        return this.#a;
    }

    set a(value: number) { // this is file
        this.#a = value;
    }

    get #b() { // Error: An accessor cannot be named with a private identifier.(18023)
        return this.a * 2;
    }

    set #b(value: number) { // Error: An accessor cannot be named with a private identifier.(18023)
        this.a = value / 2;
    }
}