How to use the formik.isNaN function in formik

it('should work properly', () => {
    (isFunction(() => {}): boolean);
    (isObject({}): boolean);
    (isInteger(1): boolean);
    (isString(''): boolean);
    (isNaN(1 / 0): boolean);
    (isEmptyChildren([]): boolean);
    (isPromise(Promise.resolve(1)): boolean);
    (isInputEvent({}): boolean);

    (getActiveElement(document): Element | null);

    getIn({ a: { b: 2 } }, ['a', 'b']);
    setIn({ a: { b: 2 } }, 'a', 3);
    setNestedObjectValues({}, 1);
  });
});

export function parseLimit(str: string) {
    const v = parseInt(str, 10);
    return !isNaN(v) ? v : null;
}