Add and remove CSS classes from elements

function get(elmnt) {
	return document.getElementById(elmnt);
}
 
function find_index(array, string) {
	var i = 0;
	for(i=0;i<array.length;i++) {
		if(array[i]==string) break;
	}
	return array[i] == string ? i : -1;
}
 
function add_class(elmnt, new_class) {
	classes = get(elmnt).className.split(' ');
	if(find_index(classes, new_class)==-1) { // new_class is not present
		classes[classes.length] = new_class;
		get(elmnt).className = classes.join(' ');
	}
}
 
function remove_class(elmnt, class_to_remove) {
	classes = get(elmnt).className.split(' ');
	class_index = find_index(classes, class_to_remove);
	if(class_index!=-1) { // class_to_remove is present
		classes.splice(class_index, 1);
		get(elmnt).className = classes.join(' ');
	}
}