js

Shadow DOM

there are times where an element requires complete encapsulation and we don’t want it to be affected by even global styles.

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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
</head>
<body>
  <span class="shadow-host">
    <a href="https://twitter.com/ireaderinokun">
      Follow @ireaderinokun 
    </a>
  </span>
  <!-- Note that we didn’t just use the <a> element as the shadow host, because certain elements, primarily interactive elements, can’t be shadow hosts. -->
  <script>
    const shadowE1 = document.querySelector(".shadow-host");
    const shadow = shadowE1.attachShadow({mode: 'open'});

    // Although the regular HTML children are viewable in the inspector, they are no longer visible on the page as the shadow root takes over.
    // Next, we want to create the content to form our new shadow tree

    const link = document.createElement("a");
    link.href = shadowE1.querySelector("a").href;
    link.innerHTML = `<span aria-label="Twittter icon"></span>
                      ${shadowE1.querySelector("a").textContent}`;
    shadow.appendChild(link);

    //Finally, we can add some styles by creating a <style> element and appending that to the shadow root too.
    
    const styles = document.createElement("style");
    styles.textContent = `
    a, span {
      vertical-align: top;
      display: inline-block;
      box-sizing: border-box;
    }

    a {
        height: 20px;
        padding: 1px 8px 1px 6px;
        background-color: #1b95e0;
        color: #fff;
        border-radius: 3px;
        font-weight: 500;
        font-size: 11px;
        font-family:'Helvetica Neue', Arial, sans-serif;
        line-height: 18px;
        text-decoration: none;   
    }

    a:hover {  background-color: #0c7abf; }

    span {
        position: relative;
        top: 2px;
        width: 14px;
        height: 14px;
        margin-right: 3px;
        background: transparent 0 0 no-repeat;
        background-image: url(data:image/svg+xml,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20viewBox%3D%220%200%2072%2072%22%3E%3Cpath%20fill%3D%22none%22%20d%3D%22M0%200h72v72H0z%22%2F%3E%3Cpath%20class%3D%22icon%22%20fill%3D%22%23fff%22%20d%3D%22M68.812%2015.14c-2.348%201.04-4.87%201.744-7.52%202.06%202.704-1.62%204.78-4.186%205.757-7.243-2.53%201.5-5.33%202.592-8.314%203.176C56.35%2010.59%2052.948%209%2049.182%209c-7.23%200-13.092%205.86-13.092%2013.093%200%201.026.118%202.02.338%202.98C25.543%2024.527%2015.9%2019.318%209.44%2011.396c-1.125%201.936-1.77%204.184-1.77%206.58%200%204.543%202.312%208.552%205.824%2010.9-2.146-.07-4.165-.658-5.93-1.64-.002.056-.002.11-.002.163%200%206.345%204.513%2011.638%2010.504%2012.84-1.1.298-2.256.457-3.45.457-.845%200-1.666-.078-2.464-.23%201.667%205.2%206.5%208.985%2012.23%209.09-4.482%203.51-10.13%205.605-16.26%205.605-1.055%200-2.096-.06-3.122-.184%205.794%203.717%2012.676%205.882%2020.067%205.882%2024.083%200%2037.25-19.95%2037.25-37.25%200-.565-.013-1.133-.038-1.693%202.558-1.847%204.778-4.15%206.532-6.774z%22%2F%3E%3C%2Fsvg%3E);
    }
    `;

    shadow.appendChild(styles);
  </script>
</body>
</html>

参考

what-is-the-shadow-dom