用js如何自定义标签

class MyElement extends HTMLElement {
  // 定义元素的属性和方法
}

customElements.define('my-element', MyElement);

<template id="my-element-template">
  <div><h1>我的自定义元素</h1></div>
</template>

MyElement.prototype.connectedCallback = function() {
  const template = document.getElementById('my-element-template');
  const clone = template.content.cloneNode(true);
  this.appendChild(clone);
};

<my-element>自定义标签内容</my-element>

class TextInputElement extends HTMLElement {
  constructor() {
    super();

    this._value = '';
  }

  static get observedAttributes() {
    return ['value'];
  }

  attributeChangedCallback(name, oldValue, newValue) {
    if (name === 'value') this._value = newValue;
  }

  connectedCallback() {
    this.render();
  }

  render() {
    this.innerHTML = `
      <input type="text" value="${this._value}">
    `;
  }
}

customElements.define('text-input', TextInputElement);

<text-input value="初始值"></text-input>