sameHeights

function sameHeights(selector) {
    var selector = selector || '[data-key="sameHeights"]',
        query = document.querySelectorAll(selector),
        elements = query.length,
        max = 0;
    if (elements) {
        while (elements--) {
            var element = query[elements];
            if (element.clientHeight > max) {
                max = element.clientHeight;
            }
        }
        elements = query.length;
        while (elements--) {
            var element = query[elements];
            element.style.height = max + 'px';
        }
    }
}

if ('addEventListener' in window) {
    window.addEventListener('onresize', function(){
        sameHeights();
    });
    window.addEventListener('load', function(){
        sameHeights();
    });
}

// Add the following to any div/element that you want to be the same size
data-key="sameHeights"