I’m working on a form that allows users to dynamically add and remove expense rows using jQuery. The issue I’m facing is with maintaining sequential indexes for each row, even after adding or removing rows.

Here’s the scenario:

The form allows users to add multiple expense rows, where each row has fields for description, expense date, and amount.
The index for each row should be sequential (e.g., 0, 1, 2, …) and should update correctly when rows are removed.

This is the html form

@model ExpenseApplication.Models.ViewModels.ExpenseFormViewModel

@using (Html.BeginForm("AddExpense", "Employee", FormMethod.Post))
{
    <div id="expenseData" data-expense-index="@Model.Expenses.Count"></div>
    <h2>Create Expense Form</h2>

    @Html.ValidationSummary(true, "", new { @class = "text-danger" })

    <div class="form-group">
        @Html.LabelFor(m => m.Currency, "Currency")
        @Html.DropDownListFor(m => m.Currency, Model.CurrencyList, "Select a currency--", new { @class = "form-control" })
        @Html.ValidationMessageFor(m => m.Currency, "", new { @class = "text-danger" })
    </div>

    <h3 class="mt-3">Expenses</h3>
    <table class="table">
        <thead>
            <tr>
                <th>Description</th>
                <th>Expense Date</th>
                <th>Amount</th>
                <th>Actions</th> 
            </tr>
        </thead>
        <tbody id="expensesTable">
            @for (int i = 0; i < Model.Expenses.Count; i++)
            {
                <tr>
                    <td>
                        @Html.TextBoxFor(m => m.Expenses[i].Description, new { @class = "form-control" })
                        @Html.ValidationMessageFor(m => m.Expenses[i].Description, "", new { @class = "text-danger" })
                    </td>
                    <td>
                        @Html.TextBoxFor(m => m.Expenses[i].ExpenseDate, new { @class = "form-control", type = "date" })
                        @Html.ValidationMessageFor(m => m.Expenses[i].ExpenseDate, "", new { @class = "text-danger" })
                    </td>
                    <td>
                        @Html.TextBoxFor(m => m.Expenses[i].Amount, new { @class = "form-control amountInput" })
                        @Html.ValidationMessageFor(m => m.Expenses[i].Amount, "", new { @class = "text-danger" })
                    </td>
                    <td>
                        <button type="button" class="btn btn-danger removeExpense">Remove</button>
                    </td>
                </tr>
            }
        </tbody>
    </table>

    <button type="button" id="addExpense" class="btn btn-primary">Add Expense</button>

    <div>
        <strong>Total Amount:</strong> <span id="totalAmount">0.00</span>
    </div>

    <div>
        <button type="submit" class="btn btn-success" id="expenseForm">Submit Expense Form</button>
    </div>
}

And here is the javascript code

var expenseIndex = $('#expensesTable tr').length;  // Initialize expenseIndex to the number of existing rows

// Add new expense row
$('#addExpense').click(function () {
    var newRow = `<tr>
                    <td><input type="text" name="Expenses[${expenseIndex}].Description" class="form-control" /></td>
                    <td><input type="date" name="Expenses[${expenseIndex}].ExpenseDate" class="form-control" /></td>
                    <td><input type="number" name="Expenses[${expenseIndex}].Amount" class="form-control amountInput" /></td>
                    <td><button type="button" class="btn btn-danger removeExpense">Remove</button></td>
                  </tr>`;
    $('#expensesTable').append(newRow);
    
    // After adding a new row, reindex all rows
expenseIndex++ 
    calculateTotal();
});

$(document).on('click', '.removeExpense', function () {
    $(this).closest('tr').remove();
    reindexExpenses();  
    calculateTotal();
});

function reindexExpenses() {
    // Reindex each row to ensure sequential indexes
    $('#expensesTable tr').each(function (index) {
        $(this).find('input').each(function () {
            let field = $(this).attr('name');
            if (field) {
                // Update the name attribute to reflect the current index
                var newName = field.replace(/Expenses[d+]/, `Expenses[${index}]`);
                $(this).attr('name', newName);
            }
        });
    });

    // Update the expenseIndex to reflect the current number of rows
    expenseIndex = $('#expensesTable tr').length;
}

// Calculate total expense amount
function calculateTotal() {
    var total = 0;
    $('.amountInput').each(function () {
        var amount = parseFloat($(this).val()) || 0;
        total += amount;
    });
    $('#totalAmount').text(total.toFixed(2));  // Update total amount display
}

// Update total amount on input change
$(document).on('input', '.amountInput', function () {
    calculateTotal();
});

// Recalculate total on page load
$(document).ready(function () {
    calculateTotal();
});

// Validate form before submission to ensure at least one expense
$('#expenseForm').click(function (e) {
    var expensesCount = $('#expensesTable tr').length;
    if (expensesCount === 0) {
        Swal.fire({
            icon: 'warning',
            title: 'No Expenses Added',
            text: 'At least one expense must be added.',
            confirmButtonText: 'OK'
        });
        e.preventDefault();  // Prevent form submission if no expenses
    }
});

The problem I’m encountering: When users add a few rows and then remove one, the new row added later does not get the correct index. For example, if the user has rows with indexes 0 and 1, and then removes the row with index 1, a new row added will have index 2 instead of 1.

• Implemented reindexing logic that updates the name attributes of inputs.
• Updated expenseIndex after adding or removing rows.
  What I need help with: I need help fixing the reindexing logic so that when rows are removed, the indexes of the remaining rows are updated correctly. Any suggestions or solutions would be greatly appreciated!