<div class="content"> <div class="section"></div> <form action="#"> <textarea id="$value"></textarea> <button type="button" id="sub">發送</button> </form></div>

.content{ border-radius: 5px; border: 2px solid #cccccc; width: 500px; height: 700px; margin: 50px auto 0; overflow: hidden; } .section{ width: 500px; height: 569px; overflow-x: hidden; overflow-y: auto; border-bottom: 1px solid #cccccc;  padding-top: 30px; } .section::-webkit-scrollbar{ display: none; } form{ width: 500px; height: 100px; } form textarea{ outline: none; border: none; display: block; float: left; width: 370px; height: 100px; font-size: 25px; text-align: top; line-height: 35px; resize: none; } form button{ outline: none; border: none; display: block; float: left; width: 130px; height: 100px; } form button:active{ background: #ccc; } .line{ width: 500px; overflow: hidden; } .left,.right{ height: auto; font-size: 25px; line-height: 50px; border-radius: 10px; padding: 0 10px; overflow-wrap: break-word; margin-bottom: 20px; } .left{ max-width: 400px; margin-left: 20px; float: left; background: rgb(243, 244, 245); } .right{ max-width: 400px; float: right; margin-right: 20px; background: rgb(79, 230, 49); }

<script type="text/javascript"> function $(str){ if (str[0]=='.') {  return document.getElementsByClassName(str.substring(1)); }else if (str[0]=='#') {  return document.getElementById(str.substring(1)); }else{  return document.getElementsByTagName(str);  } } //以上代碼可以單獨封裝成一個函數 var count = 0; $('#sub').onclick=function(){ //當點擊發送按鈕后，創建class名為line的盒子，來盛放聊天的內容 var div = document.createElement('div'); div.className = 'line'; $('.section')[0].appendChild(div); var str = $('#$value').value; var p = document.createElement('p'); if (count%2==1) {  p.className = 'left'; }else{  p.className = 'right'; } p.innerHTML = str; $('#$value').value = ''; div.appendChild(p); count++; } </script>