原生js判断是否有某个class，如果有就删掉，没有加上

判断是否有某个class，如果有就删掉，没有加上
<style>
    #div1 {width: 100px;height: 100px;position: absolute;}
    .div1{background:red;}
    .div2{background:yellow;}
</style>

    <div id="div1" class="div2 div1 div3 div2"></div>

    <script>
    var oDiv1 = document.getElementById("div1");

    oDiv1.onclick = function() {
        hasClass(this,"div2")
    }

    function hasClass(obj,sClass) {
        var oldClass = obj.className;
        var re = new RegExp(‘\\b‘ + sClass + ‘\\b‘);
        if (re.test(oldClass)) {
            obj.className=obj.className.split(sClass).join("").replace(/\s+$/,"")
        } else {
            obj.className = oldClass +" "+ sClass
        }
    }
    </script>