无名啊

<link rel="stylesheet" href="https://fonts.googleapis.com/icon?family=Material+Icons">
<script>

  const blocks = {
    userimg: {type: 'img', icon: 'image'},
    iframe_box: {type: 'iframe', icon: 'web'},
    audio_box: {type: 'audio', icon: 'audiotrack'},
    video_box: {type: 'video', icon: 'movie'},
  };

  function formatSize(size) {
    const i = size && Math.floor(Math.log(size) / Math.log(1024));
    return (size / (1 << (10 * i))).toFixed(i && 2) + ' ' + ' KMGT'[i].trim() + 'B';
  }

  customElements.define('my-button', class extends HTMLElement {
    #ref = {};
    #orig_node;
    #media_src;
    #media_node;

    #createElementFromObject(obj) {
      let el = document.createElement(obj.tag);
      for (const k in obj) {
        if (k === 'children')
          obj.children.forEach(c => el.appendChild(this.#createElementFromObject(c)));
        else if (k === 'text')
          el.textContent = obj[k];
        else if (k === 'ref')
          this.#ref[obj[k]] = el;
        else if (k !== 'tag')
          el.setAttribute(k, obj[k]);
      }
      return el;
    }

    constructor() {
      super();

      // 创建一个 shadow root
      let shadow = this.attachShadow({mode: 'open'});

      [
        {tag: 'link', rel: 'stylesheet', href: 'https://unpkg.com/material-components-web@latest/dist/material-components-web.min.css'},
        {tag: 'link', rel: 'stylesheet', href: 'https://fonts.googleapis.com/icon?family=Material+Icons'},
        {tag: 'script', src: 'https://unpkg.com/material-components-web@latest/dist/material-components-web.min.js'},
        {tag: 'button', class: 'mdc-fab mdc-fab--extended', style: 'margin: 10px', children: [
            {tag: 'div', class: 'mdc-fab__ripple'},
            {tag: 'span', class: 'material-icons mdc-fab__icon', ref: 'icon'},
            {tag: 'span', class: 'mdc-fab__label', ref: 'text'},
          ]},
        {tag: 'style', text: `
          :host {
            /* --mdc-theme-primary: #e74c3c; */
            --mdc-theme-secondary: #fafafa;
            /* --mdc-theme-background: #f00; */
            /* --mdc-theme-on-primary: #fff; */
            --mdc-theme-on-secondary: #2c3e50;
          }
        `},
      ].forEach(x => shadow.appendChild(this.#createElementFromObject(x)));

      this.onclick = this.recover;
    }

    get text() {
      return this.#ref.text.textContent;
    }

    set text(s) {
      this.#ref.text.textContent = s;
    }

    get icon() {
      return this.#ref.icon.textContent;
    }

    set icon(s) {
      this.#ref.icon.textContent = s;
    }

    // onclick() {  // 为什么不能这样重写方法？？
    recover() {
      this.#media_node.src &&= this.#media_src;
      this.parentNode.replaceChild(this.#orig_node, this);
      delete this;
    }

    // 替换掉旧节点，展示本按钮
    replace(root_node, media_node) {
      this.#orig_node = root_node.parentNode.replaceChild(this, root_node);
      this.#media_node = media_node;
      this.#media_src = media_node.src;
      media_node.src &&= ' ';

      // 询问目标链接大小，太大则等待用户选择，较小直接显示
      if (this.#media_src) {
        fetch(this.#media_src, {method: 'HEAD'}).then(resp => {
          if (resp.ok) {
            const size = parseInt(resp.headers.get('content-length'));
            if (size < (1 << 20) && this.icon === blocks.userimg.icon)
              this.recover();
            else if (size > 0)
              this.text += `（${formatSize(size)}）`;
          }
        });
      }
    }
  });

  document.addEventListener('DOMContentLoaded', () => {
    document.querySelectorAll(Object.keys(blocks).map(x => `.${x}`).join()).forEach(x => {

      // 获取 element 类型、显示按钮时的图标
      const {type, icon} = Object.entries(blocks).find(([k]) => x.classList.contains(k))[1];

      // 若图片已下载完毕，就让它显示吧
      if (type === 'img' && x.complete)
        return;

      // 获取真正的多媒体节点
      const media_node = ['audio', 'video'].includes(type) ? x.querySelector(type) : x;

      // 图片有外层链接，则准备替换整个外层
      if (type === 'img' && x.parentNode.href)
        x = x.parentNode;

      // 创建按钮
      let el = document.createElement('my-button');
      el.icon = icon;
      el.text = type === 'iframe' ? '内嵌网页' : media_node.alt || media_node.src;
      el.replace(x, media_node);
    });
  });
</script>