AngularJS fixed header scrollable table directive

26 February 2014

This post contains a custom AngularJS directive you can use to give your html table a fixed header and footer with a scrollable body, we developed it for a law firm marketing website recently, it uses a pure CSS approach and doesn't touch any of the html tags, leaving the html table completely intact and happily semantic :)

Creating a fixed header scrollable table using purely CSS turns out to be a surprisingly tricky thing to do, in an ideal world I thought it would just be a matter of setting the height of the table body and "overflow:hidden", but there turns out to be a bit more to it than that, especially if you have a table that contains dynamic content because the width of each column in the thead and tbody need to be set in order for it to continue looking like a table and not just a big mess.

In a nutshell the CSS changes that need to happen are:

  • Set the width of each column in the thead and tbody, making sure they match up so the columns aren't wonky
  • Set the thead and tbody to "display:block;"
  • Set the tbody height and "overflow:auto;" to add the scrollbar
  • When there's a scrollbar (when the tbody content overflows it's height), reduce the width of the final column in the tbody by the width of the scrollbar

Here's the solution I came up with:

The fixedHeader AngularJS directive

/**
 * AngularJS fixed header scrollable table directive
 * @author Jason Watmore <jason@pointblankdevelopment.com.au> (http://jasonwatmore.com)
 * @version 1.2.0
 */
(function () {
    angular
        .module('anguFixedHeaderTable', [])
        .directive('fixedHeader', fixedHeader);

    fixedHeader.$inject = ['$timeout'];

    function fixedHeader($timeout) {
        return {
            restrict: 'A',
            link: link
        };

        function link($scope, $elem, $attrs, $ctrl) {
            var elem = $elem[0];

            // wait for data to load and then transform the table
            $scope.$watch(tableDataLoaded, function(isTableDataLoaded) {
                if (isTableDataLoaded) {
                    transformTable();
                }
            });

            function tableDataLoaded() {
                // first cell in the tbody exists when data is loaded but doesn't have a width
                // until after the table is transformed
                var firstCell = elem.querySelector('tbody tr:first-child td:first-child');
                return firstCell && !firstCell.style.width;
            }

            function transformTable() {
                // reset display styles so column widths are correct when measured below
                angular.element(elem.querySelectorAll('thead, tbody, tfoot')).css('display', '');

                // wrap in $timeout to give table a chance to finish rendering
                $timeout(function () {
                    // set widths of columns
                    angular.forEach(elem.querySelectorAll('tr:first-child th'), function (thElem, i) {

                        var tdElems = elem.querySelector('tbody tr:first-child td:nth-child(' + (i + 1) + ')');
                        var tfElems = elem.querySelector('tfoot tr:first-child td:nth-child(' + (i + 1) + ')');

                        var columnWidth = tdElems ? tdElems.offsetWidth : thElem.offsetWidth;
                        if (tdElems) {
                            tdElems.style.width = columnWidth + 'px';
                        }
                        if (thElem) {
                            thElem.style.width = columnWidth + 'px';
                        }
                        if (tfElems) {
                            tfElems.style.width = columnWidth + 'px';
                        }
                    });

                    // set css styles on thead and tbody
                    angular.element(elem.querySelectorAll('thead, tfoot')).css('display', 'block');

                    angular.element(elem.querySelectorAll('tbody')).css({
                        'display': 'block',
                        'height': $attrs.tableHeight || 'inherit',
                        'overflow': 'auto'
                    });

                    // reduce width of last column by width of scrollbar
                    var tbody = elem.querySelector('tbody');
                    var scrollBarWidth = tbody.offsetWidth - tbody.clientWidth;
                    if (scrollBarWidth > 0) {
                        // for some reason trimming the width by 2px lines everything up better
                        scrollBarWidth -= 2;
                        var lastColumn = elem.querySelector('tbody tr:first-child td:last-child');
                        lastColumn.style.width = (lastColumn.offsetWidth - scrollBarWidth) + 'px';
                    }
                });
            }
        }
    }
})();

 

Sample HTML that uses the fixed-header directive

<table class="table table-bordered" fixed-header>
    <thead>
        <tr>
            <th>Header 1</th>
            <th>Header 2</th>
            <th>Header 3</th>
            <th>Header 4</th>
        </tr>
    </thead>
    <tbody>
        <tr ng-repeat="item in [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]">
            <td>Row {{item}} Col 1</td>
            <td>Row {{item}} Col 2</td>
            <td>Row {{item}} Col 3</td>
            <td>Row {{item}} Col 4</td>
        </tr>
    </tbody>
    <tfoot>
        <tr>
            <td>Footer 1</td>
            <td>Footer 2</td>
            <td>Footer 3</td>
            <td>Footer 4</td>
        </tr>
    </tfoot>
</table>

The default height of the table body is 400px, to change this add a table-height attribute to the table element eg: table-height="500px".

UPDATE 08/10/2014: Added support for fixed footer (tfoot) element.