How to add case insensitive sorting in react table?

//function to sort the results
    function filterCaseInsensitive(filter, row) {
        const id = filter.pivotId || filter.id;
        return (
            row[id] !== undefined ?
                String(row[id].toLowerCase()).startsWith(filter.value.toLowerCase())
            :
                true
        );
    }

    // react table code goes here
    <ReactTable
        data={data}
        columns={columns}
        filterable
        defaultFilterMethod={(filter, row) => filterCaseInsensitive(filter, row) }
    />

For case insensitive and numbers sorting pass sortTypes in table props like this:

useTable({
    sortTypes: {
                alphanumeric: (row1, row2, columnName) => {
                    const rowOneColumn = row1.values[columnName];
                    const rowTwoColumn = row2.values[columnName];
                    if (isNaN(rowOneColumn)) {
                        return rowOneColumn.toUpperCase() >
                            rowTwoColumn.toUpperCase()
                            ? 1
                            : -1;
                    }
                    return Number(rowOneColumn) > Number(rowTwoColumn) ? 1 : -1;
                }
            }
})

The question mentions sorting but links to filtering. For custom sorting the app's owner mentions on Github to pass a sortTypes: { alphanumeric: MyCustomFunc } in the table props, like this:

useTable({
  columns,
  sortTypes: {
    alphanumeric: (row1, row2, columnName) => {
      return compareIgnoreCase(
        row1.values[columnName],
        row2.values[columnName]
      )
    },
  },
},
useSortBy

)