HTML

<div class="wrapper">
    <i class="avatar"></i>
    <textarea id="tx" placeholder="发一条友善的评论" rows="2" maxlength="200"></textarea>
    <button>发布</button>
  </div>
  <div class="wrapper">
    <span class="total">0/200字</span>
  </div>
  <div class="list">
    <div class="item" style="display: none;">
      <i class="avatar"></i>
      <div class="info">
        <p class="name">清风徐来</p>
        <p class="text">大家都辛苦啦，感谢各位大大的努力，能圆满完成真是太好了[笑哭][支持]</p>
        <p class="time">2022-10-10 20:29:21</p>
      </div>
    </div>
  </div>

CSS

.wrapper {
      min-width: 400px;
      max-width: 800px;
      display: flex;
      justify-content: flex-end;
    }

    .avatar {
      width: 48px;
      height: 48px;
      border-radius: 50%;
      overflow: hidden;
      background: url(./images/avatar.jpg) no-repeat center / cover;
      margin-right: 20px;
    }

    .wrapper textarea {
      outline: none;
      border-color: transparent;
      resize: none;
      background: #f5f5f5;
      border-radius: 4px;
      flex: 1;
      padding: 10px;
      transition: all 0.5s;
      height: 30px;
    }

    .wrapper textarea:focus {
      border-color: #e4e4e4;
      background: #fff;
      height: 50px;
    }

    .wrapper button {
      background: #00aeec;
      color: #fff;
      border: none;
      border-radius: 4px;
      margin-left: 10px;
      width: 70px;
      cursor: pointer;
    }

    .wrapper .total {
      margin-right: 80px;
      color: #999;
      margin-top: 5px;
      opacity: 0;
      transition: all 0.5s;
    }

    .list {
      min-width: 400px;
      max-width: 800px;
      display: flex;
    }

    .list .item {
      width: 100%;
      display: flex;
    }

    .list .item .info {
      flex: 1;
      border-bottom: 1px dashed #e4e4e4;
      padding-bottom: 10px;
    }

    .list .item p {
      margin: 0;
    }

    .list .item .name {
      color: #FB7299;
      font-size: 14px;
      font-weight: bold;
    }

    .list .item .text {
      color: #333;
      padding: 10px 0;
    }

    .list .item .time {
      color: #999;
      font-size: 12px;
    }

JS

//获取文本域
  const tx = document.querySelector('#tx')
  //获取字数统计
  const total = document.querySelector('.total')
  //获取要显示的文本
  const text = document.querySelector('.text')
  //整个要显示的区域
  const item = document.querySelector('.item')
  //当文本域聚焦时，字数统计显示
  tx.addEventListener('focus',function(){
    total.style.opacity = 1
  })
  //当文本域失焦时，字数统计隐藏
  tx.addEventListener('blur',function(){
    total.style.opacity = 0
  })
  //文本域输入内容时统计字数
  tx.addEventListener('input',function(){
    total.innerHTML = `${tx.value.length}/200字`
  })

  //回车键弹起，把内容添加到需要显示的区域
  tx.addEventListener('keyup',function(e){
    if(e.key === 'Enter'){
      if(tx.value.trim() !== ''){
      text.innerHTML = tx.value.trim()
      item.style.display = 'block'
    }
      tx.value = ''
    }
  })