Wed 20 Feb 2008

I’ve been using JQuery for a while now and really agree with its tag line that it’s the “The Write Less, Do More, JavaScript Library”. We’ve also got this code for dragging and dropping table rows that has proved very popular, so it seemed natural to combine the two and wrap up the table drag and drop as a JQuery plugin.

Update: You can now read the latest docs at https://github.com/isocra/TableDnD

Why have another plugin?

Dragging and dropping rows within a table can’t be handled by general purpose drag and drop utilities for a number of reasons, not least because you need to move the whole row, not just the cell that receives the mouse events. Re-parenting the row also requires specific code. Sadly also, effects like fadeIn and fadeOut don’t work well with table rows on all browsers, so we have to go for simpler effects.

What does it do?

This TableDnD plugin allows the user to reorder rows within a table, for example if they represent an ordered list (tasks by priority for example). Individual rows can be marked as non-draggable and/or non-droppable (so other rows can’t be dropped onto them). Rows can have as many cells as necessary and the cells can contain form elements.

How do I use it?

  1. Download Download jQuery (version 1.2 or above), then the TableDnD plugin (current version 0.7).
  2. Reference both scripts in your HTML page in the normal way.
  3. In true jQuery style, the typical way to initialise the tabes is in the $(document).ready function. Use a selector to select your table and then call tableDnD(). You can optionally specify a set of properties (described below).
1 One some text
2 Two some text
3 Three some text
4 Four some text
5 Five some text
6 Six some text

The HTML for the table is very straight forward (no Javascript, pure HTML):

<table id="table-1" cellspacing="0" cellpadding="2" >
    <tr id="1"><td>1</td><td>One</td><td>some text</td></tr>
    <tr id="2"><td>2</td><td>Two</td><td>some text</td></tr>
    <tr id="3"><td>3</td><td>Three</td><td>some text</td></tr>
    <tr id="4"><td>4</td><td>Four</td><td>some text</td></tr>
    <tr id="5"><td>5</td><td>Five</td><td>some text</td></tr>
    <tr id="6"><td>6</td><td>Six</td><td>some text</td></tr>
</table>

To add in the “draggability” all we need to do is add a line to the $(document).ready(...) function
as follows:

<script type="text/javascript">
$(document).ready(function() {
    <span class="comment">// Initialise the table</span>
    $("#table-1").tableDnD();
});
</script>

In the example above we’re not setting any parameters at all so we get the default settings. There are a number of parameters you can set in order to control the look and feel of the table and also to add custom behaviour on drag or on drop. The parameters are specified as a map in the usual way and are described below:

onDragStyle
This is the style that is assigned to the row during drag. There are limitations to the styles that can be associated with a row (such as you can’t assign a border—well you can, but it won’t be displayed). (So instead consider using onDragClass.) The CSS style to apply is specified as a map (as used in the jQuery css(...) function).
onDropStyle
This is the style that is assigned to the row when it is dropped. As for onDragStyle, there are limitations to what you can do. Also this replaces the original style, so again consider using onDragClass which is simply added and then removed on drop.
onDragClass
This class is added for the duration of the drag and then removed when the row is dropped. It is more flexible than using onDragStyle since it can be inherited by the row cells and other content. The default is class is tDnD_whileDrag. So to use the default, simply customise this CSS class in your stylesheet.
onDrop
Pass a function that will be called when the row is dropped. The function takes 2 parameters: the table and the row that was dropped. You can work out the new order of the rows by using
table.tBodies[0].rows.
onDragStart
Pass a function that will be called when the user starts dragging. The function takes 2 parameters: the table and the row which the user has started to drag.
scrollAmount
This is the number of pixels to scroll if the user moves the mouse cursor to the top or bottom of the window. The page should automatically scroll up or down as appropriate (tested in IE6, IE7, Safari, FF2, FF3 beta)

This second table has has an onDrop function applied as well as an onDragClass. The javascript to set this up is as follows:

$(document).ready(function() {

    // Initialise the first table (as before)
    $("#table-1").tableDnD();

    // Make a nice striped effect on the table
    $("#table-2 tr:even').addClass('alt')");

    // Initialise the second table specifying a dragClass and an onDrop function that will display an alert
    $("#table-2").tableDnD({
        onDragClass: "myDragClass",
        onDrop: function(table, row) {
            var rows = table.tBodies[0].rows;
            var debugStr = "Row dropped was "+row.id+". New order: ";
            for (var i=0; i<rows.length; i++) {
                debugStr += rows[i].id+" ";
            }
            $('#debugArea').html(debugStr);
        },
        onDragStart: function(table, row) {
            $('#debugArea').html("Started dragging row "+row.id);
        }
    });
});
1 One
2 Two
3 Three
4 Four
5 Five
6 Six
7 Seven
8 Eight
9 Nine
10 Ten
11 Eleven
12 Twelve
13 Thirteen
14 Fourteen

What to do afterwards?

Generally once the user has dropped a row, you need to inform the server of the new order. To do this, we’ve added a method called serialise(). It takes no parameters but knows the current table from the context. The method returns a string of the form <em>tableId</em>[]=<em>rowId1</em>&<em>tableId</em>[]=<em>rowId2</em>&<em>tableId</em>[]=<em>rowId3</em>...
You can then use this as part of an Ajax load.

This third table demonstrates calling the serialise function inside onDrop (as shown below). It also demonstrates the “nodrop” class on row 3 and “nodrag” class on row 5, so you can’t pick up row 5 and
you can’t drop any row on row 3 (but you can drag it).

$('#table-3').tableDnD({
    onDrop: function(table, row) {
        alert($.tableDnD.serialize());
    }
});

Ajax result

Drag and drop in this table to test out serialise and using JQuery.load()

1 One
2 Two
3 Three (Can’t drop on this row)
4 Four
5 Five (Can’t drag this row)
6 Six

This table has multiple TBODYs. The functionality isn’t quite working properly. You can only drag the rows inside their own TBODY, you can’t drag them outside it. Now this might or might not be what you want, but unfortunately if you then drop a row outside its TBODY you get a Javascript error because inserting after a sibling doesn’t work. This will be fixed in the next version. The header rows all have the classes “nodrop” and “nodrag” so that they can’t be dragged or dropped on.

H1 H2 H3
4.1 One
4.2 Two
4.3 Three
4.4 Four
4.5 Five
4.6 Six
H1 H2 H3
5.1 One
5.2 Two
5.3 Three
5.4 Four
5.5 Five
5.6 Six
H1 H2 H3
6.1 One
6.2 Two
6.3 Three
6.4 Four
6.5 Five
6.6 Six

The following table demonstrates the use of the default regular expression. The rows have IDs of the form table5-row-1, table5-row-2, etc., but the regular expression is /[^-]*$/ (this is the same as used in the NestedSortable plugin for consistency). This removes everything before and including the last hyphen, so the serialised string just has 1, 2, 3 etc. You can replace the regular expression by setting the serializeRegexp option, you can also just set it to null to stop this behaviour.

$('#table-5').tableDnD({
    onDrop: function(table, row) {
        alert($('#table-5').tableDnDSerialize());
    },
    dragHandle: ".dragHandle"
});
1 One some text
2 Two some text
3 Three some text
4 Four some text
5 Five some text
6 Six some text

In fact you will notice that I have also set the dragHandle on this table. This has two effects: firstly only the cell with the drag handle class is draggable and secondly it doesn’t automatically add the cursor: move style to the row (or the drag handle cell), so you are responsible for setting up the style as you see fit.

Here I’ve actually added an extra effect which adds a background image to the first cell in the row whenever you enter it using the jQuery hover function as follows:

$("#table-5 tr").hover(function() {
      $(this.cells[0]).addClass('showDragHandle');
}, function() {
      $(this.cells[0]).removeClass('showDragHandle');
});

This provides a better visualisation of what you can do to the row and where you need to go to drag it (I hope).