原生js获取&添加&删除class

function getClass(parent, className, tagName) {  
    var aEle = parent.getElementsByTagName(tagName || "*");
    var arr = [];
    for (var i = 0; i < aEle.length; i++) {
        var aName = aEle[i].className.split(" ")
        for (var j = 0; j < aName.length; j++) {
            if (aName[j] == className) {
                arr.push(aEle[i])
                break;
            }
        }
    }
    return arr;
}

function addClass(obj, className) {  
    if (obj.className == " ") {
        obj.className = className;
    } else {
        var _index = arrIndex(obj.className.split(" "), className)
        if (_index == -1) {
            obj.className += " " + className;
        }
    }
}

function removeClass(obj, className) {
    if (obj.className != " ") {
        var aClass = obj.className.split(" ");
        var _index = arrIndex(aClass, className);
        if (_index != -1) {
            aClass.splice(_index, 1)
            obj.className = aClass.join(" ");
        }
    }
}

function arrIndex(arr, v) {
    for (var i = 0; i < arr.length; i++) {
        if (arr[i] == v) {
            return i;
        }
    }
    return -1;
}