for loop execute slow for large data

I have a for loop that take too long for execute for large amount of data:

for (var itm = 0; itm < itmCount; itm++) {

    var curObj = $('[aria-describedby=' + gridName + '_' + columnNames[itm].name + ']');

    var thisCell = $('#' + gridName + '_' + columnNames[itm].name + ' div');
    $('#widthTest').html(thisCell.text()).css({
    'font-family': thisCell.css('font-family'),
    'font-size': thisCell.css('font-size'),
    'font-weight': thisCell.css('font-weight')
    });
    var maxWidth = Width = $('#widthTest').elementRealWidth() + 17;

    var itm2Count = curObj.length;
            // Loop through Rows
            for (var itm2 = 0; itm2 < itm2Count; itm2++) {

            var thisCell = $(curObj[itm2]);

            $('#widthTest').html(thisCell.html()).css({
            'font-family': thisCell.css('font-family'),
            'font-size': thisCell.css('font-size'),
            'font-weight': thisCell.css('font-weight')
            });

            thisWidth = $('#widthTest').elementRealWidth();
            if (thisWidth > maxWidth) {maxWidth = thisWidth+10;}
            }

    $('#' + gridName + ' .jqgfirstrow td:eq(' + itm + '), #' + gridName + '_' + columnNames[itm].name).width(maxWidth).css('min-width', maxWidth+17);
    $('#' + gridName + ' .jqgfirstrow td:eq(' + 0 + '), #' + gridName + '_' + columnNames[0].name).width('30').css('min-width', '30px');

I get this issue from firefox: A script on this page may be busy, or it may have stopped responding. You can stop the script now, open the script in the debugger, or let the script continue.

and the chrome kills the page. Any idea?