function vert (elem) {
    var el = document.getElementsByTagName(elem);
    for (var i=0; i < el.length; i++) {
        var ex = el[i].childNodes[0];
        if (el[i].nodeType === 1) {
            el[i].innerHTML = el[i].innerHTML.split('').join('<br/>');
        };
    }; 
}

vert('th');

Make  TABLE TH element's innerHTML vertical

javascript

JavaScript