解决classList兼容性替代方案

//添加class
DOMTokenList.prototype.adds = function(tokens) {
    tokens.split(" ").forEach(function(token) {
        this.add(token);
   }.bind(this));
   return this;
};

var clList = document.body.classList;
clList.adds("child1 child2 child3").toString(); // "a b c child1 child2 child3"

//移除class
DOMTokenList.prototype.removes = function(tokens) {
    tokens.split(" ").forEach(function(token) {
        this.remove(token);
    }.bind(this));
return this;
};

var clList = document.body.classList;
clList.removes("child1 child2 child3").toString(); // "a b c child1 child2 child3"