Typescript pass property by reference

I have a Typescript class with 4 different properties, like this:

class MyClass {
     private x: number;
     private y: number;
     private z: number;
     private w: number;
}

I want to create four functions that increment these properties:

   incrementX() { this.x++; }
   incrementY() { this.y++; )
   ...

However, I don't want the increment logic (++) to be duplicated, I want to place it in one function. If Typescript had ref parameters like C#, I would do something like:

   incrementX() { this.increment(ref this.x); }
   increment(p: ref number) { p++; }

Typescript does not support passing by reference. The non type-safe way of implementing this is:

   incrementX() { this.increment("x"); }
   increment(p: string) {
       const self = this as any;
       self[p]++;
   }

It's not type-safe. I can easily call increment('not-a-property') without getting an error from the compiler. I've added a runtime check to make sure self[p] is indeed a number, but I still want something the compiler can catch.

Is there a type-safe way of implementing this?

Note: obviously my actual code doesn't increment numbers, but rather does something quite elaborate - not on numbers but on another class type.

You could use keyof and number extends maybe? To allow passing only keys of the class which are numbers.

Playground here

class MyClass {
  public a: number = 0;
  public b: number = 0;
  public c: string = "";

  public increment(
     key: {
      [K in keyof MyClass]-?: number extends MyClass[K] ? K : never
    }[keyof MyClass]
  ) {
    this[key]++;
  }
}

const test = new MyClass();

test.increment("a");
test.increment("b");
test.increment("c"); // fail
test.increment("d"); // fail