JSONLike type in TypeScript

Serializable.ts

type JSONLike =
    | { [property: string]: JSONLike }
    | readonly JSONLike[]
    | string
    | number
    | boolean
    | null;

interface Serializable {
    toJSON(): JSONLike;
}

class MyClass implements Serializable {
    map = new Map<string, string>();

    toJSON() {
        // return this.map; Error
        return Object.fromEntries(this.map.entries())
    }
}