function hasClass(ele,cls) {
return ele.className.match(new RegExp('(\\s|^)'+cls+'(\\s|$)'));
}

function addClass(ele,cls) {
if (!this.hasClass(ele,cls)) ele.className += " "+cls;
}

function removeClass(ele,cls) {
if (hasClass(ele,cls)) {
var reg = new RegExp('(\\s|^)'+cls+'(\\s|$)');
ele.className=ele.className.replace(reg,' ');
}
}

//call the functions
addClass(document.getElementById("test"), "test");
removeClass(document.getElementById("test"), "test")
if(hasClass(document.getElementById("test"), "test")){//do something};