Unhandled Promise Rejection: TypeError: Spread syntax requires …iterable not be null or undefined [closed]

There is an array. Using the forEach() function, I want to list all the elements of this array, and then use the push() method to add other elements to it. However, why does the error “Unhandled Promise Rejection: TypeError: Spread syntax requires …iterable not be null or undefined” appear? Please tell me what I’m doing wrong.

const townList = computed(() => {
    const items: Town[] = [];
    filtredList.value.forEach((group) => {
      items.push(...group.towns);
    });
    return items;
});

When checking the array, Postman outputs the data.