Calculate Field Values Dynamically

function onChange(control, oldValue, newValue, isLoading, isTemplate) {
  // Exit if form is loading
  if (isLoading) {
    return;
  }

  // Example 1: Calculate total cost (quantity × unit price)
  var quantity = parseFloat(g_form.getValue('u_quantity')) || 0;
  var unitPrice = parseFloat(g_form.getValue('u_unit_price')) || 0;
  var totalCost = quantity * unitPrice;

  // Set the calculated total with proper formatting
  g_form.setValue('u_total_cost', totalCost.toFixed(2));

  // Optional: Show currency formatted value
  if (totalCost > 0) {
    var formattedTotal = '$' + totalCost.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
    g_form.showFieldMsg('u_total_cost', 'Total: ' + formattedTotal, 'info');
  }

  // Example 2: Calculate percentage
  // Uncomment to enable
  /*
  var completed = parseFloat(g_form.getValue('u_completed_items')) || 0;
  var total = parseFloat(g_form.getValue('u_total_items')) || 1;  // Avoid division by zero
  var percentage = (completed / total) * 100;

  g_form.setValue('u_completion_percentage', percentage.toFixed(1));
  */

  // Example 3: Calculate days between dates
  // Uncomment to enable
  /*
  var startDate = g_form.getValue('u_start_date');
  var endDate = g_form.getValue('u_end_date');

  if (startDate && endDate) {
    var start = new Date(startDate);
    var end = new Date(endDate);

    // Calculate difference in days
    var diffTime = Math.abs(end - start);
    var diffDays = Math.ceil(diffTime / (1000 * 60 * 60 * 24));

    g_form.setValue('u_duration_days', diffDays);
    g_form.showFieldMsg('u_duration_days', diffDays + ' days between dates', 'info');
  }
  */

  // Example 4: Calculate discount and final price
  // Uncomment to enable
  /*
  var originalPrice = parseFloat(g_form.getValue('u_original_price')) || 0;
  var discountPercent = parseFloat(g_form.getValue('u_discount_percent')) || 0;

  var discountAmount = originalPrice * (discountPercent / 100);
  var finalPrice = originalPrice - discountAmount;

  g_form.setValue('u_discount_amount', discountAmount.toFixed(2));
  g_form.setValue('u_final_price', finalPrice.toFixed(2));
  */

  // Example 5: Calculate average
  // Uncomment to enable
  /*
  var value1 = parseFloat(g_form.getValue('u_value_1')) || 0;
  var value2 = parseFloat(g_form.getValue('u_value_2')) || 0;
  var value3 = parseFloat(g_form.getValue('u_value_3')) || 0;

  var average = (value1 + value2 + value3) / 3;
  g_form.setValue('u_average', average.toFixed(2));
  */

  // Example 6: Calculate age from date of birth
  // Uncomment to enable
  /*
  var dob = g_form.getValue('u_date_of_birth');
  if (dob) {
    var birthDate = new Date(dob);
    var today = new Date();

    var age = today.getFullYear() - birthDate.getFullYear();
    var monthDiff = today.getMonth() - birthDate.getMonth();

    if (monthDiff < 0 || (monthDiff === 0 && today.getDate() < birthDate.getDate())) {
      age--;
    }

    g_form.setValue('u_age', age);
  }
  */
}