<script>
function on(name) {
var elements = document.getElementsByClassName(name);
for (var i = 0; i < elements.length; i++) {
var elem = elements[i];
elem.style.backgroundColor = "pink";
}
}
function off(name) {
var elements = document.getElementsByClassName(name);
for (var i = 0; i < elements.length; i++) {
var elem = elements[i];
elem.style.backgroundColor = "white";
}
}
</script>