</label>
    <input type="button" id="btn" value="  "/>
    <button id="calc" onclick="calc()">  </button>

    <script type="text/javascript">
        var box = document.getElementById("box");
        var ul = document.createElement("ul");
        box.appendChild(ul);
        var btn = document.getElementById("btn");
        var msg = document.getElementById("msg");
        var n = 0;
        btn.onclick = function(){
            if(msg.value === ""){
                alert("     ")
            } else{
                n++;
                var li = document.createElement("li");
                li.innerHTML = msg.value + "  "+"<span>X</span>";
                var lis = document.getElementsByTagName("li");
                if(n === 1){
                    ul.appendChild(li);
//                              appendChild
                }else{
                    ul.insertBefore(li,lis[0]);
//                                
                }
                msg.value = "";
//                     
                var span = document.getElementsByTagName("span");
                for(var i = 0;i<span.length;i++){
                    span[i].onclick = function(){
                        ul.removeChild(this.parentNode);
                        n--;
                    }
                }
            }
        };
        function calc(){
            alert("   "+n+"   ")
        }
    </script>
</code></pre> 
    </div> 
   </div> 
   <p> </p> 
  </div> 
  <p>   :https://www.cnblogs.com/tarantino/p/8796934.html</p> 
 </div> 
</div>
                            </div>
                        </div>