解决classList兼容性替代方案

//添加classDOMTokenList.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classDOMTokenList.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"