Filter and Summarize

Totals Footer

Quantity and price columns are multiplied per row and then reduced into a table footer total.

Program

CSV-backed tables can show both source rows and computed summaries. The footer should come from data, not hand-entered totals.

totals_footer.html 
<script>
  const rows = [
    { item: "Cable", qty: 3, price: 12.50 },
    { item: "Hub", qty: 1, price: 39.00 }
  ];
  const lineTotals = rows.map(row => row.qty * row.price);
  const total = lineTotals.reduce((sum, value) => sum + value, 0);
  renderWithFooter(rows, total);
</script>
map map derives one computed value for each source row.
reduce reduce combines many values into one summary value.