在 MVC4 上向 DOM 表添加行的问题

Question

I have a "DOM" list in MVC 4 using jQuery to add elements dynamically but at the moment of removing all the elements The table no longer allows me to add more elements, I have tried to use length and comparisons but it does not work.

Am probably missing something obvious but can't see what it is. Any ideas?

Example

Here is my table code

    <div><a href="#" id="addNew"><img src="~/Images/splus.png" alt="Add Product" style="border:0"/></a></div>
        <table id="dataTable" border="0" cellpadding="0" cellspacing="0">
            <thead>
            <tr>
                <th></th>
                <th></th>
               <th>Product</th>
                <th>Quantity</th>
                <th></th>
            </tr>
                </thead>
            <tbody>
            @if (Model != null && Model.Count > 0)
            {
                int j = 0;
                int index = 1;
                foreach (var i in Model)
                {
                   <tr>
                        <td>@index</td>
                        <td>@Html.HiddenFor(a => a[j].SEQ_NO, new { id = "nrow", Value = index })</td>
                        <td>@Html.DropDownList("PRODUCTS", "Select Product")</td>
                        <td>@Html.TextBoxFor(a => a[j].QUANTITY)</td>                 
                        <td>   
                                <a href="#" id="remove" class="remove"><img src="~/Images/sminus.png" alt="Add Product" style="border:0"/></a>    
                        </td>                      
                   </tr>
                    index += 1;
                    j++;
                }
            }
         </tbody>
        </table>

Here is my jQuery Code when i click on Add New

            $("#addNew").click(function (e) {
            e.preventDefault();
            var last = $('#dataTable>tbody>tr:last');
            if (last.length > 0) {
                var name = last.children().find('input,select')[0].name;
                var index = Number(name.replace(/[^0-9]/gi, '')) + 1;
                var tr = ('<tr>' + last.html().replace(/[0-9]+__/gi, index + '__') + '</tr>').replace(/\[[0-9]+\]+[.]/gi, '[' + index + '].');
                numberRows($('#dataTable tbody').append(tr));
             }

            });

UPDATE:

Add "REMOVE CODE"

            $(document).on('click', '#remove', function (e) {
            e.preventDefault();
            $(this).parent().parent().remove();
            numberRows($('#dataTable tbody'));

        });

Answer 1

Am probably missing something obvious but can't see what it is. Any ideas?

var name = last.children().find('input,select')[0].name;

This line of code requires one last child, which means after you removed the last under, the name will be undefined. In fact, the Add New function won't even pass the if (last.length > 0) since when the last got removed, the last.length becomes 0.

You can debug in devtools, and will see:

BEFORE the last got removed:

AFTER the last got removed:

Thus, to fix this issue, the simplest solution is to not remove the last but hide it. Please check below code:

    $(document).on('click', '#remove', function (e) {
        e.preventDefault();
        if ($('#dataTable>tbody>tr').length > 1) {
            $(this).parent().parent().remove();
            //numberRows($('#dataTable tbody'));
        }
        else {
            $(this).parent().parent().hide();
        }
    });

Ps. Not sure what happens in numberRows() function so I commented it.