function getElementsByClass(klass, tag){
    var result = [];
    var elems = document.getElementsByTagName(tag);
    for(var i = 0; i < elems.length; ++i){
        if(elems[i].className == klass){
            result.push(elems[i]);
        }
    }
    return result;
}

function make_bar_onmousedown(){
    var flag = 0;
    return function(e){
        if(!e) e = event;
        var elem = e.srcElement || e.target;
        elem.style.backgroundColor = flag ? "#baa" : "#fff";
        flag = !flag;
    }
}

function init(){
    var elems = getElementsByClass('bar', 'div');
    for(var i = 0; i < elems.length; ++i){
        elems[i].onmousedown = make_bar_onmousedown();
    }
}

window.onload = init;