How to Implement a cascader using Web Component-Toy模板网

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To implement a cascader using Web Components, you can create a custom element that encapsulates the cascader functionality. Here’s an example:

<!DOCTYPE html>
<html>
<head>
  <style>
    .cascader {
      display: inline-block;
      position: relative;
    }

    .cascader input[type="text"] {
      width: 200px;
    }

    .cascader .dropdown {
      position: absolute;
      top: 100%;
      left: 0;
      z-index: 1;
      background-color: #fff;
      border: 1px solid #ccc;
      border-top: none;
      display: none;
    }

    .cascader .dropdown ul {
      list-style-type: none;
      padding: 0;
      margin: 0;
    }

    .cascader .dropdown ul li {
      padding: 8px;
      cursor: pointer;
    }

    .cascader .dropdown ul li:hover {
      background-color: #f5f5f5;
    }
  </style>
</head>
<body>
  <cascader></cascader>

  <script>
    class Cascader extends HTMLElement {
      constructor() {
        super();

        const shadow = this.attachShadow({ mode: 'open' });

        const container = document.createElement('div');
        container.classList.add('cascader');

        const input = document.createElement('input');
        input.type = 'text';
        input.addEventListener('focus', () => {
          this.showDropdown();
        });

        const dropdown = document.createElement('div');
        dropdown.classList.add('dropdown');

        const ul = document.createElement('ul');
        ul.addEventListener('click', (event) => {
          const selectedValue = event.target.textContent;
          input.value = selectedValue;
          this.hideDropdown();
          this.dispatchEvent(new CustomEvent('valueChange', { detail: selectedValue }));
        });

        const li1 = document.createElement('li');
        li1.textContent = 'Option 1';
        const li2 = document.createElement('li');
        li2.textContent = 'Option 2';
        const li3 = document.createElement('li');
        li3.textContent = 'Option 3';

        ul.appendChild(li1);
        ul.appendChild(li2);
        ul.appendChild(li3);

        dropdown.appendChild(ul);

        container.appendChild(input);
        container.appendChild(dropdown);

        shadow.appendChild(container);
      }

      showDropdown() {
        const dropdown = this.shadowRoot.querySelector('.dropdown');
        dropdown.style.display = 'block';
      }

      hideDropdown() {
        const dropdown = this.shadowRoot.querySelector('.dropdown');
        dropdown.style.display = 'none';
      }
    }

    customElements.define('cascader', Cascader);

    const cascader = document.querySelector('cascader');
    cascader.addEventListener('valueChange', (event) => {
      const selectedValue = event.detail;
      console.log('Selected value:', selectedValue);
    });
  </script>
</body>
</html>

In the above example, we define a custom element called cascader using the customElements.define() method. Inside the Cascader class, we extend the HTMLElement class to create our custom element.

In the constructor, we create a shadow DOM using attachShadow({ mode: 'open' }). The shadow DOM encapsulates the internal structure and styling of the custom element.

We create a <div> element with the class cascader to act as the container for the cascader component.

Inside the container, we create an <input> element of type text to display the selected value and handle the focus event to show the dropdown.

We also create a html file:

<div class="dropdown">
  <ul>
    <li>Option 1</li>
    <li>Option 2</li>
    <li>Option 3</li>
  </ul>
</div>

The dropdown is initially hidden with the CSS rule display: none;. When the input element receives focus, the showDropdown() method is called, which sets the display property of the dropdown to block, making it visible.

The dropdown contains an unordered list (<ul>) with list items (<li>) representing the options. When an option is clicked, the valueChange event is dispatched with the selected value as the event detail. The input element’s value is updated with the selected value, and the dropdown is hidden using the hideDropdown() method.

To use the cascader component, you can simply add the <cascader></cascader> element to your HTML. You can listen for the valueChange event and retrieve the selected value using JavaScript.

Here’s an example of how you can listen for the valueChange event:

<!DOCTYPE html>
<html>
<head>
</head>
<body>
  <cascader></cascader>

  <script>
    const cascader = document.querySelector('cascader');
    cascader.addEventListener('valueChange', (event) => {
      const selectedValue = event.detail;
      console.log('Selected value:', selectedValue);
    });
  </script>
</body>
</html>

In the above example, we select the cascader element using document.querySelector(). We then add an event listener to listen for the valueChange event. When the event is triggered, we retrieve the selected value from the event detail and log it to the console.

You can customize the appearance and behavior of the cascader by modifying the CSS and JavaScript code according to your requirements.文章来源地址https://www.toymoban.com/news/detail-826270.html

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