实现添加功能时，第一次增加一个，第二次增加两个，求大佬帮助。我只想每次增加一个

• 
  测试1
  
  


• 
  测试2
  
  


• 
  测试3
  
  

    <div class="main ">
        <section class="conactive ">测试内容1</section>
        <section>测试内容2</section>
        <section>测试内容3</section>
    </div>
</div>

$(function() {
    //定义一个tab类
    var that;
    class Tab {
        constructor(id) {
            // this.main = $(id);
            that = this;
            this.main = $(id);
            this.add = this.main.find('.add');
            this.iconguanbi = this.main.find('.icon-guanbi');
            this.lis = this.main.find('li');
            this.sections = this.main.find('section');
            this.init();
        }
        init() {
                // 初始化操作，相关元素绑定事件
                // console.log(this);
                this.get();
                this.lis.on('click', this.toggleTab);
                this.add.on('click', this.addTab);

                this.iconguanbi.on('click', this.deleteTab);
            }
            //切换功能
        toggleTab() {
            console.log(this);
            that.clear();
            var index = $(this).index();
            $(this).addClass('active');
            that.sections.eq(index).addClass('conactive').siblings().removeClass('conactive');
        }

        //清除操作
        clear() {
                this.lis.removeClass('active');
                this.sections.removeClass('conactive');
            }
            //添加功能
        addTab() {
                that.clear();

                var li = $('<li><span></span>' + '测试' + '<span class=" iconfont icon-guanbi "></span></li>');
                li.addClass('active');
                that.lis.parents('ul').append(li);
                // console.log(that.lis.parents('ul').length);
                that.sections.parents('.main').append('<section class="conactive">测试内容</section>')

                that.init();
            }
            //删除功能
        deleteTab() {
                that.sections.eq($(this).parents('li').index()).remove();
                $(this).parents('li').remove();
                that.init();
            }
            //修改功能
        editTab() {}
            //获取所有li，section
        get() {
            this.lis = this.main.find('li');
            this.sections = this.main.find('section');

        }
    }
    new Tab("#tabsbox");
    // tab.init();
})