function change(id) {

    var tars = document.getElementsByName("daohang");
    var i = 0;
    for (i; i < tars.length; i++) {
        tars[i].className = "";
        tars[i].childNodes[0].className = "";
    }

    document.getElementById(id).className = "right";
    document.getElementById(id).childNodes[0].className = "left";
}