Web Components are reusable custom HTML elements natively supported by the browser, including 1. Custom Elements: Create custom tags such as ; 2. Shadow DOM: implement style and DOM isolation; 3. HTML Templates: Use

Web Components is a web development technology that allows you to create reusable custom HTML elements. They are natively supported by the browser and do not need to rely on any frameworks (such as React or Vue), which means you can use them directly in native JavaScript and can be reused in different projects.

Simply put, it allows you to build page functions like building blocks.

1. What parts does Web Components contain?

Web Components mainly consist of three core technologies:

• Custom Elements : Custom HTML tags, such as <my-button></my-button> .
• Shadow DOM : Creates a separate DOM and style environment for the component to avoid style conflicts.
• HTML Templates : Use <template></template> and <slot></slot> to render on demand.

Combining these three can create a well-packaged and well-structured component.

For example: If you want to make a button component with a unified style, use Web Components, you can define a <fancy-button></fancy-button> tag, whose style and behavior are encapsulated inside, and no matter which page you use it on, it will not be affected by external CSS.

2. How to create a simple Web Component?

The steps to create a Web Component are not complicated:

• Define class inheritance HTMLElement
• Register components using customElements.define()
• Optionally use Shadow DOM and Template

 class MyButton extends HTMLElement {
  constructor() {
    super();
    this.attachShadow({ mode: 'open' });
    this.shadowRoot.innerHTML = `
      <style>
        button {
          background: blue;
          color: white;
          padding: 10px;
        }
      </style>
      <button><slot></slot></button>
    `;
  }
}

customElements.define(&#39;my-button&#39;, MyButton);

Then you can use it like this:

 <my-button>Click me</my-button>

The style of this button is not affected by the CSS of the outside page, as it is rendered in the Shadow DOM.

3. Advantages and applicable scenarios of Web Components

• Cross-frame compatibility : Because it is natively supported by the browser, it can be embedded and used regardless of whether you use Vue, React or jQuery.
• Style isolation : Shadow DOM makes component styles more controllable and not easy to "fight".
• Lightweight and dependency-free : no additional libraries or frameworks are required, suitable for micro front-end or plug-in systems.

Common uses include:

• Build basic components in the design system (such as buttons, input boxes)
• Develop third-party embedded widgets (such as statistics codes, advertising slots)
• Unified UI component standards when collaborating with multiple teams

4. Some notes when using Web Components

Although Web Components are powerful, there are some details to note:

• Browser compatibility : Modern mainstream browsers basically support it, but if you still need to support IE11, you may need Polyfill.
• Debugging is a little bit troublesome : Due to the use of Shadow DOM, some style debugging is not as intuitive as ordinary elements.
• It needs to be adapted when integrating with the framework : For example, React does not recognize custom elements by default, and additional configuration is required.

If you want to make the component stronger, you can also add property listening, lifecycle methods (connectedCallback, disconnectedCallback, etc.) to handle logic.

Basically that's it. Although Web Components is not a new concept, it is becoming more and more practical in the modern front-end ecosystem, especially when you want to "write once and use everywhere".

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