How to access static members from instance methods in typescript?

Question

I try to use a static member from an instance method. I know about accessing static member from non-static function in typescript, but I do not want to hard code the class to allow inheritance:

class Logger {
  protected static PREFIX = '[info]';

  public log(msg: string) {
    console.log(Logger.PREFIX + ' ' + msg); // What to use instead of Logger` to get the expected result?
  }
}

class Warner extends Logger {
  protected static PREFIX = '[warn]';
}

(new Logger).log('=> should be prefixed [info]');
(new Warner).log('=> should be prefixed [warn]');

I've tried things like

typeof this.PREFIX

TLDR - ClassName.property. For overridden properties, (<typeof ClassName> this.constructor).property. — nathanfranke
– nathanfranke, Commented Oct 2, 2020 at 18:56
These days you should use (this.constructor as typeof ClassName).property which is equivalent but the more modern syntax — Maccesch
– Maccesch, Commented Nov 17, 2024 at 16:08

Michael Cook · Accepted Answer · 2024-06-14 15:28:36Z

45

You simply need ClassName.property :

class Logger {
  protected static PREFIX = '[info]';
  public log(message: string): void {
    alert(Logger.PREFIX + message); 
  }
}

class Warner extends Logger {
  protected static PREFIX = '[warn]';
}

MORE

from : https://basarat.gitbook.io/typescript/future-javascript/classes

TypeScript classes support static properties that are shared by all instances of the class. A natural place to put (and access) them is on the class itself and that is what TypeScript does:

class Something {
    static instances = 0;
    constructor() {
        Something.instances++;
    }
}

var s1 = new Something();
var s2 = new Something();
console.log(Someting.instances); // 2

UPDATE

If you want it to inherit from the particular instance's constructor use this.constructor. Sadly you need to use some type assertion. I am using typeof Logger shown below:

class Logger {
  protected static PREFIX = '[info]';
  public log(message: string): void {
    var logger = <typeof Logger>this.constructor; 
    alert(logger.PREFIX + message); 
  }
}

class Warner extends Logger {
  protected static PREFIX = '[warn]';
}

edited Jun 14, 2024 at 15:28

Michael Cook

1,7072 gold badges27 silver badges49 bronze badges

answered Mar 24, 2015 at 22:42

basarat

278k60 gold badges475 silver badges528 bronze badges

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

10 Comments

Simon Hürlimann Over a year ago

I know about using the ClassName.property. But then it will use Logger.PREFIX even in subclasses that have their own .PREFIX defined.

Simon Hürlimann Over a year ago

Updated the question to be more clear about the expected result.

basarat Over a year ago

@SimonHürlimann Updated the answer to take that into account ;)

Jimmy Kane Over a year ago

This does not work. For example: ``` const a = new Logger(); a.log('a ') const b = new Warner(); b.log('b ') ``` Both log Info

Long Nguyen Over a year ago

Why this answer is voted up? Warner instance printed out [info]

|

Collectives™ on Stack Overflow

How to access static members from instance methods in typescript?

1 Answer 1

10 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

10 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related