Declare recursivley method chaining in TypeScript

Question

I have the following object in vanilla JS:

const obj = {
  foo(val) {
    console.log('foo:', val);
    return this;
  }
  bar(val) {
    console.log('bar:', val);
    return this;
  }
}

And I want to decalre this object in my .d.ts file but I'm not sure what is the best way to define a type for recursive method chaining..

Can someone help with this implementation?

Answer 1

You can define this in a TypeScript interface:

interface Obj {
    [key: string]: (val: string) => this
}

const obj: Obj = {
  foo(val) {
    console.log('foo:', val);
    return this;
  },
  bar(val) {
    console.log('bar:', val);
    return this;
  }
}

I've assumed that the val arguments are string.

Edit: I've just seen your comment on your post - you can capture the key dynamically with [key: string] . I've updated my answer.