[Vuejs]-How do I properly strongly-type a reactive array whose elements are interfaced Class objects?

I ended up being able to use the following code to create a reactive array with interfaced objects:

let salesContainer = reactive({
      sales: [] as SalesData[],
});

However, now, in order to access the data, I’d need to use:

salesContainer.sales[0].

I was trying to come up with a solution where I could simply do :

salesContainer[0]; 

Is there a better solution than what I have?

EDIT with better(?) solution:

let salesContainer: SalesData[] = reactive([]);

function buildSalesData() {
  for (let i = 0; i < state.posts.length; i++) {
    salesContainer.push(
      new SalesData(
        state.posts[i].ds_store_id,
        state.posts[i].ds_amt,
        state.posts[i].ds_qty,
        state.posts[i].ds_dept
      )
    );
  }
}

This seems to work fine!