<input type="text" id="input">
    <button id="btn">添加</button>
    <ul id="list">
        <li>吃饭</li>
        <li>睡觉</li>
        <li>打豆豆</li>
    </ul>

    <script>
        var oInput=document.getElementById('input')
        var oBtn=document.getElementById('btn')
        var oList=document.getElementById('list')
        //按钮事件监听
        oBtn.onclick=function(){
          //创建新的元素li标签
          var oLi= document.createElement('li')
           oLi.innerHTML=oInput.value
          //上树
          oList.appendChild(oLi)
        }
        //给ul绑定点击事件
        oList.onclick=function(e){
            //删除点击的这项元素
            oList.removeChild(e.target)
        }
    </script>