console 命令行工具 X clear
console
<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .container {
      position: relative;
    }

    .content {
      position: absolute;
    }
  </style>
</head>

<body onload="main()">
  <div class="container">
    <template>
      <span>天地玄黄 宇宙洪荒 日月盈昃 辰宿列张 寒来暑往 秋收冬藏 闰馀成岁 律吕调阳 云腾致雨 露结为霜 金生丽水 玉出昆冈 剑号巨阙 珠称夜光 果珍李柰 菜重芥姜 海咸河淡 鳞潜羽翔 龙师火帝 鸟官人皇 始制文字 乃服衣裳</span>
      <img style="height:20px;" src="https://static.segmentfault.com/main_site_next/9cb17c82/_next/static/media/logo-b.1ef53c6e.svg" />
    </template>
    <div class="content"> </div>
  </div>
  <script>
    function main() {
      const template = document.querySelector('template');
      const target = document.querySelector('.container .content');
      target.innerHTML = template.innerHTML;
      const span = target.querySelector('.container .content span');
      const spanText = span.innerHTML;

      var index = spanText.length;

      const myResizeObserver = new ResizeObserver(entries => {
        for (let entry of entries) {
          onchange(true)
        }
      });

      myResizeObserver.observe(target);

      // 创建一个 MutationObserver 实例，传入回调函数
      const myMutationObserver = new MutationObserver((mutationsList, myMutationObserver) => {
        for (let mutation of mutationsList) {
          onchange(false)
        }
      });

      // 配置观察器，监视子元素变化和属性变化
      const config = { childList: true, attributes: true };
      myMutationObserver.observe(span, config);

      function onchange(reset) {
        console.log(reset, index)
        if (reset) {
          index = spanText.length
        }

        if (target.clientHeight > 45) {
          index = index - 1
          span.innerHTML = spanText.slice(0, index) + '…'
        } else {
          if (reset) {
            if (index < spanText.length) {
              span.innerHTML = spanText.slice(0, index) + '…'
            } else {
              span.innerHTML = spanText
            }
          }
          target.style.position = 'relative'
        }
      }
    }
  </script>
</body>

</html>