sorts a table by rows with no dependencies

tablesort.css

th[data-sort] { 
  cursor: n-resize; 
  -webkit-touch-callout: none;
  -webkit-user-select: none;
  -khtml-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  user-select: none;
}

th:after {
  color: #999;
  font-weight: normal;
  font-size: 0.8em;
  margin-left: 0.15em;
  content: '\25b2';
  visibility: hidden;
}

th[data-sort-dir="1"]:after {
  content: '\25b2';
  visibility: visible;
}

th[data-sort-dir="-1"]:after {
  content: '\25bc';
  visibility: visible;
}

tablesort.js

(function() {

    'use strict';

    var basicSort = function ( a, b ) {

        if ( !isNaN( a ) && !isNaN( b ) ) {
            a = +a;
            b = +b;
        }

        if ( typeof a == 'string' && typeof b == 'string' ) {
            a = a.toLowerCase();
            b = b.toLowerCase();
        }

        if ( a > b ) return 1;

        if ( a < b ) return -1;

        return 0;
    };

    Array.prototype.slice.call(document.querySelectorAll('th[data-sort]'), 0)
        .forEach(function(el, index) {

            if (! el.tbl) {
                var tbl = el.parentNode;
                while (tbl.tagName != 'TABLE') {
                    tbl = tbl.parentNode;
                }
                tbl.setAttribute('data-sort-dir', 1);
                el.tbl = tbl;
            }

            Array.prototype.slice.call(el.tbl.querySelectorAll('th'), 0)
                .forEach(function(h, colIndex) {
                    if (h == el) el.setAttribute('data-index', colIndex);
                });

            el.addEventListener('click', function(e) {

                var asc = +el.tbl.getAttribute('data-sort-dir'),
                    rows = Array.prototype.slice.call(el.tbl.querySelectorAll('tbody tr'), 0),
                    bdy = el.tbl.querySelector('tbody');

                Array.prototype.slice.call(el.tbl.querySelectorAll('th[data-sort-dir]'), 0)
                    .forEach(function(h) {
                        h.removeAttribute('data-sort-dir');
                    });

                el.tbl.setAttribute('data-sort-index', el.getAttribute('data-index'));
                el.tbl.setAttribute('data-sort-dir', asc * -1);

                el.setAttribute('data-sort-dir', asc);

                rows.sort(function(a, b) {
                    var idx = el.tbl.getAttribute( 'data-sort-index' ),
                        fn = function ( _ ) {
                            if ( !_ ) return '';
                            return _.getAttribute('data-sort-by') || _.textContent;
                        },
                        a2 = fn(a.querySelectorAll('td')[idx]),
                        b2 = fn(b.querySelectorAll('td')[idx]);

                    return basicSort(a2, b2) * asc;
                });

                while (bdy.firstChild) {
                    bdy.removeChild(bdy.firstChild);
                }

                rows.forEach(function(r, i) { bdy.appendChild(r); });
            });
        });

})();