<!-- chat box -->
  <div class="chat">
    <div class="messages">
      <ul id="messages">
        <li><div class="message">Message 1</div></li>
        <li><div class="message">Message 2</div></li>
        <li><div class="message">Message 3</div></li>
        <li><div class="message">Message 4</div></li>
        <li><div class="message">Message 5</div></li>
        <li><div class="message">Message 6</div></li>
        <li><div class="message">Message 7</div></li>
        <li><div class="message">Message 8</div></li>
        <li><div class="message">Message 9</div></li>
        <li><div class="message">Message 10</div></li>
      </ul>
    </div>
    <input type="text" class="input"  id="input" placeholder="Enter your message" required >
    <div class="prompt">Press enter to send</div>
  </div>
  <!-- newsfeed -->
  <div class="container">
    <ul class="feed">
      <li><div class="card">Card 1</div></li>
      <li><div class="card">Card 2</div></li>
      <li><div class="card">Card 3</div></li>
      <li><div class="card">Card 4</div></li>
      <li><div class="card">Card 5</div></li>
      <li class="nested">
        <ul>
          <li><div class="card">Card A</div></li>
          <li><div class="card">Card B</div></li>
          <li><div class="card">Card C</div></li>
        </ul>
      </li>
      <li><div class="card">Card 6</div></li>
      <li><div class="card">Card 7</div></li>
      <li><div class="card">Card 8</div></li>
      <li><div class="card">Card 9</div></li>
      <li><div class="card">Card 10</div></li>
    </ul>
  </div>

@import url('https://fonts.googleapis.com/css?family=Roboto:300,400');

* { 
  box-sizing: border-box; 
}

body {
    font-family: Arial, Helvetica, sans-serif;
    font-size: 14px;
    margin: 0;
	  background-color: grey;
}

ul {
  margin: 0;
  padding: 0;
  list-style: none outside none;
}

.container {
	max-width: 800px;
	margin: 0 auto;
}

.card {
	background-color: #fff;
	padding: 10px;
	margin: 10px;
	min-height: 300px;
}

.feed {
  display: flex;
  flex-wrap: wrap;
}

@supports (display: flex) and (display: contents) {
  .feed ul,
  .feed li {
    display: contents;
  }

  .card {
    flex: 1 0 40%;
  }
}

@supports (display: flex) and (not (display: contents)) {
  .feed li {
    flex: 1 0 50%;
  }

  .feed li.nested {
    flex-basis: 100%;
  }

  .feed li.nested ul {
    display: flex;
    flex-wrap: wrap;
  }
}

// Chat Style
.chat {
  background: #fff;
  border: 10px solid #000;
  bottom: 0;
  font-size: 10px;
  position: fixed;
  right: 0;
  width: 300px;
  z-index: 1001;
}

.messages {
  border-bottom: 5px solid #000;
  overflow: auto;
  padding: 0;
  max-height: 0;
  transition: max-height 500ms;
  overscroll-behavior-y: contain;
}

.message {
  background: #000;
  border-radius: 5px;
  color: #fff;
  margin: 0 20% 10px 0;
  padding: 10px;
}

.messages li:last-child .message {
  margin-bottom: 0;
}

.input {
  border: none;
  display: block;
  padding: 10px;
  width: 100%;
}

.chat:focus-within .messages {
  max-height: 300px;
  padding: 10px;
}

.chat:focus-within ~ .container {
  filter: blur(5px);
}

.prompt {
		line-height: 2em;
		max-height: 0;
		overflow: hidden;
		padding: 0 10px;
		text-align: right;
		transition: max-height 500ms; 
}
.input:not(:placeholder-shown) + .prompt {
 		max-height: 2em; 
}

.message--mine {
		background: #ff2089;
		margin-left: 20%;
		margin-right: 0;
	}

// 获取相应的元素
const input = document.getElementById('input');
const messages = document.getElementById('messages');

// 监听input的键盘事件
input.addEventListener('keypress', (event) => {
    // 检查是否按下Enter键
    if (event.keyCode === 13) {
        // 检查字段是否有效
        if (input.validity.valid) {
            // 使用该值创建DOM元素
            const message = createMessage(input.value);
            // 将新创建的DOM元素添加到消息列表
            messages.appendChild(message);
            // 清除输入框的值
            input.value = '';
            // 滚动到消息列表的底部
            messages.parentNode.scrollTop = messages.parentNode.scrollHeight;
        }
    }
});

// 将input的值转换为HTML的字符串
function createMessage (value) {
    return stringToDom(`<li><div class="message">${value}</div></li>`)
}

// 将字符串转换为真实的DOM
function stringToDom (string) {
    const template = document.createElement('template');
    template.innerHTML = string.trim();
    return template.content.firstChild;
}