class myDialog extends HTMLElement {
  // ...
  connectedCallback() {
    const shadowRoot = this.attachShadow({ mode: 'open' });
    shadowRoot.innerHTML = `
      <div class="dialog">
        <div class="dialog-content">
          <div class="dialog-body">
            彈窗內(nèi)容
          </div>
 
          <button id="okBtn">確定</button>
        </div>
      </div>
    `;
     shadowRoot.querySelector('#okBtn').addEventListener('click', () => {
      // 組件內(nèi)部定義事件
      this.dispatchEvent(new CustomEvent('okBtnFn'));
    });
  }
} 
customElements.define('my-dialog', myDialog);

<my-dialog></my-dialog> 
<script>
  export default {
    created() {
      document.addEventListener('okBtnFn', function(){
        // 點(diǎn)擊彈窗按鈕，觸發(fā)回調(diào)事件
      });
    }
  }
</script>

class MyIcon extends HTMLElement {
    static get observedAttributes() { return ['name','size','color'] }
    constructor() {
        super();
        const shadowRoot = this.attachShadow({ mode: 'open' });
        shadowRoot.innerHTML = `
            <svg class="icon" id="icon" aria-hidden="true" viewBox="0 0 1024 1024">
                <use id="use"></use>
            </svg>        
    } 
    attributeChangedCallback (name, oldValue, newValue) {
        if( name == 'name' && this.shadowRoot){
            // 如果使用的項(xiàng)目中，根目錄沒有 icon.svg 文件，那就 gg
            this.use.setAttributeNS('http://www.w3.org/1999/xlink', 'xlink:href', `./icon.svg#icon-${newValue}`);
        }
    }
}
customElements.define('my-icon', MyIcon);

// web component
class InputAge extends HTMLElement {
  constructor() {
    super();
  }  
// connect component
  connectedCallback() {
    const shadow = this.attachShadow({ mode: 'closed' });
    shadow.innerHTML = `<input type="number" placeholder="age" min="18" max="120" />`;
  }
}
// register component
customElements.define( 'input-age', InputAge );

<form id="myform">
  <input type="text" name="your-name" placeholder="name" />
  <input-age name="your-age"></input-age>
 
  <button>submit</button>
</form>
 
<script>
 const form = document.getElementById('myform');
 
  form.addEventListener('submit', e => {
    
    e.preventDefault();
    console.log('Submitted data:');
 
    const data = new FormData(form);
    for (let nv of data.entries()) {
      console.log(`  ${ nv[0] }: ${ nv[1] }`);
    }
 
  });
</script>