VS Code to autocomplete JavaScript class 'this' properties automatically(react-etc.net)

  const args = parseCliFlags({
    help: {
      parser: Boolean,
      description: 'whether to show help',
      short: 'h',
    },
    custom: {
      parser: (v: string) => {return {hmmm: 'yes'}},
      repeated: true
    }
  });
  if (args.help) {
    console.log('help screen!');
  }
  for (const custom of args.custom) {
    console.log(custom.hmmm);
  }

  interface Descriptor {
    readonly parser: (value: string) => any;
    readonly description?: string;
    readonly short?: string;
    readonly repeated?: true;
  }
  interface Descriptors {
    readonly [flag: string]: Descriptor;
  }
  type FlagTypes<T> = { [K in keyof T]: FlagTypeOf<T[K]> };
  type ReturnTypeOf<V> = V extends (...args: any[])=>infer R ? R : never;
  type FlagTypeOf<V> = V extends {repeated: true, parser: (val: string)=> infer R} ? R[] : V extends {parser: (val: string)=> infer R} ? R : never;