intlNumberFormatES5UseGrouping.ts(2,34): error TS2322: Type 'string' is not assignable to type 'boolean | undefined'.
intlNumberFormatES5UseGrouping.ts(3,34): error TS2322: Type 'string' is not assignable to type 'boolean | undefined'.


==== intlNumberFormatES5UseGrouping.ts (2 errors) ====
    new Intl.NumberFormat('en-GB', { useGrouping: true });
    new Intl.NumberFormat('en-GB', { useGrouping: 'true' }); // expect error
                                     ~~~~~~~~~~~
!!! error TS2322: Type 'string' is not assignable to type 'boolean | undefined'.
    new Intl.NumberFormat('en-GB', { useGrouping: 'always' }); // expect error
                                     ~~~~~~~~~~~
!!! error TS2322: Type 'string' is not assignable to type 'boolean | undefined'.
    
    const { useGrouping } = new Intl.NumberFormat('en-GB').resolvedOptions();
    