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`<style>-embedded CSS styles translate this sentence into English`

Author：Chuan Chen 阅读数：36267人阅读 分类： HTML

The <style> tag is an HTML element used to define embedded CSS styles, allowing developers to write CSS rules directly within an HTML document without the need to reference an external stylesheet. This approach is suitable for small projects or rapid prototyping but may be less maintainable and reusable for large-scale projects.

Basic Syntax of the <style> Tag

The <style> tag is typically placed in the <head> section of an HTML document but can also be included in the <body>. Its basic syntax is as follows:

<style>
  /* CSS rules go here */
  body {
    background-color: #f0f0f0;
  }
</style>

This tag does not require any attributes to function but can include the type attribute (though it is no longer necessary in HTML5):

<style type="text/css">
  /* Legacy syntax */
</style>

Attributes of the <style> Tag

While the <style> tag often requires no attributes, it supports several useful ones:

  1. media: Specifies the media type for which the stylesheet applies.
  2. scoped (deprecated): Limits styles to the parent element and its children.
  3. title: Defines an alternative stylesheet title.
<style media="print">
  /* Styles for printing */
  body {
    font-size: 12pt;
  }
</style>

Priority of Embedded Styles

Embedded styles (defined via the <style> tag) have higher priority than external stylesheets but lower priority than inline styles (defined via the style attribute). CSS priority rules are as follows:

  1. Inline styles (highest priority)
  2. Embedded styles
  3. External styles
  4. Browser default styles (lowest priority)
<head>
  <link rel="stylesheet" href="external.css"> <!-- External styles -->
  <style>
    p {
      color: blue; /* Overrides the p color in external.css */
    }
  </style>
</head>
<body>
  <p style="color: red;">This text is red</p> <!-- Inline styles have highest priority -->
</body>

Media Queries and the <style> Tag

The <style> tag can be combined with media queries to create responsive designs:

<style>
  /* Base styles */
  body {
    background-color: white;
  }
  
  /* Small-screen devices */
  @media (max-width: 600px) {
    body {
      background-color: lightblue;
    }
  }
  
  /* Print styles */
  @media print {
    body {
      font-size: 12pt;
      color: black;
    }
    .no-print {
      display: none;
    }
  }
</style>

The <style> Tag and CSS Variables

CSS variables (custom properties) can be defined and used within the <style> tag:

<style>
  :root {
    --main-color: #4CAF50;
    --secondary-color: #8BC34A;
  }
  
  body {
    background-color: var(--main-color);
  }
  
  button {
    background-color: var(--secondary-color);
  }
</style>

Dynamically Modifying <style> Content

JavaScript can dynamically modify the content of the <style> tag:

<style id="dynamic-style">
  /* Initial styles */
  body {
    background-color: white;
  }
</style>

<script>
  // Modify styles
  document.getElementById('dynamic-style').innerHTML = `
    body {
      background-color: darkblue;
      color: white;
    }
  `;
</script>

Performance Considerations for the <style> Tag

While embedded styles can reduce HTTP requests, they may pose issues in large projects:

  1. Cannot be cached by the browser
  2. Increase HTML document size
  3. Reduce style reusability
  4. May lead to code duplication
<!-- Not recommended -->
<style>
  /* Lots of duplicate styles */
  .button1 { /* ... */ }
  .button2 { /* ... */ }
  /* Dozens of similar button styles */
</style>

<!-- Better approach: Use CSS classes -->
<style>
  .btn {
    /* Base button styles */
  }
  .btn-primary {
    /* Primary button variant */
  }
</style>

The <style> Tag and Shadow DOM

In web components, the <style> tag can be used for Shadow DOM style encapsulation:

<template id="my-component">
  <style>
    /* These styles only apply within the Shadow DOM */
    p {
      color: red;
    }
  </style>
  <p>This text is red</p>
</template>

<script>
  class MyComponent extends HTMLElement {
    constructor() {
      super();
      const template = document.getElementById('my-component');
      const templateContent = template.content;
      
      this.attachShadow({mode: 'open'})
        .appendChild(templateContent.cloneNode(true));
    }
  }
  
  customElements.define('my-component', MyComponent);
</script>

Alternatives to the <style> Tag

While the <style> tag is convenient, other methods may be more suitable in certain cases:

  1. External stylesheets (<link rel="stylesheet">) for large projects
  2. CSS-in-JS solutions (e.g., styled-components) for frameworks like React
  3. Inline styles (style attribute) for dynamic styling
<!-- External stylesheet -->
<link rel="stylesheet" href="styles.css">

<!-- CSS-in-JS example (React) -->
<script type="text/javascript">
  const StyledDiv = styled.div`
    color: ${props => props.color};
  `;
</script>

<!-- Inline styles -->
<div style="color: red;"></div>

Practical Use Cases for the <style> Tag

A common use case is adding one-off styles for a specific page:

<!DOCTYPE html>
<html>
<head>
  <title>Special Page</title>
  <style>
    /* Page-specific styles */
    .special-header {
      background: linear-gradient(to right, #ff8a00, #da1b60);
      color: white;
      padding: 2rem;
      text-align: center;
    }
    
    .feature-card {
      border: 1px solid #ddd;
      border-radius: 8px;
      padding: 1rem;
      margin: 1rem 0;
      box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    }
    
    @media (max-width: 768px) {
      .special-header {
        padding: 1rem;
      }
    }
  </style>
</head>
<body>
  <header class="special-header">
    <h1>Welcome to Our Special Page</h1>
  </header>
  
  <div class="feature-card">
    <h2>Featured Function</h2>
    <p>Description of our featured function...</p>
  </div>
</body>
</html>

Combining the <style> Tag with CSS Preprocessors

While the <style> tag typically contains pure CSS, it can be combined with preprocessors via build tools:

<!-- Original HTML -->
<style lang="scss">
  /* SCSS syntax can be used here */
  $primary-color: #3bbfce;
  
  body {
    color: $primary-color;
    
    .container {
      width: 100%;
    }
  }
</style>

<!-- After build tool processing -->
<style>
  body {
    color: #3bbfce;
  }
  body .container {
    width: 100%;
  }
</style>

Browser Support and Compatibility for the <style> Tag

The <style> tag is fully supported in all modern browsers, including:

  • Chrome
  • Firefox
  • Safari
  • Edge
  • Opera
  • Internet Explorer 9+

For older browsers, note the following:

  1. IE8 and earlier have limited support for certain CSS3 features
  2. Some mobile browsers may impose size limits on the <style> tag
<!-- Conditional comments for older IE versions -->
<!--[if IE]>
<style>
  /* IE-specific styles */
  .box {
    display: inline-block;
    zoom: 1;
  }
</style>
<![endif]-->

Best Practices for the <style> Tag

To use the <style> tag effectively, follow these practices:

  1. Keep embedded styles concise; use external files for complex styles
  2. Add comments to explain styles
  3. Avoid overly specific selectors
  4. Consider using CSS methodologies (e.g., BEM) to organize styles
  5. Use embedded styles during development but consider extracting to external files before production
<style>
  /* Main container styles */
  .main-container {
    max-width: 1200px;
    margin: 0 auto;
  }
  
  /* Card component - BEM naming */
  .card {
    /* Base styles */
  }
  .card--featured {
    /* Featured variant */
  }
  .card__title {
    /* Title element */
  }
</style>

The <style> Tag and Content Security Policy (CSP)

When using Content Security Policy (CSP), embedded styles may require special handling:

<!-- Regular page without CSP -->
<style>
  /* Styles work normally */
</style>

<!-- Page with CSP -->
<meta http-equiv="Content-Security-Policy" content="style-src 'self' 'unsafe-inline'">
<!-- 'unsafe-inline' is required for embedded styles -->

Using the <style> Tag in HTML Emails

Support for the <style> tag in HTML emails is limited:

<!-- Best practices for HTML emails -->
<style type="text/css">
  /* Base styles */
  body {
    font-family: Arial, sans-serif;
  }
  /* Inline styles are still needed as fallback */
</style>

<!-- Also provide inline styles -->
<p style="font-family: Arial, sans-serif;">Text content</p>

The <style> Tag and Print Styles

Styles specifically designed for printing can be placed in the <style> tag:

<style>
  /* Screen styles */
  body {
    font-size: 16px;
  }
  
  /* Print styles */
  @media print {
    body {
      font-size: 12pt;
    }
    .no-print {
      display: none;
    }
    a::after {
      content: " (" attr(href) ")";
    }
  }
</style>

The <style> Tag in Single-Page Applications (SPAs)

In SPAs, the <style> tag can be used for component-level styling:

<!-- Vue single-file component example -->
<template>
  <div class="component">
    <!-- Component content -->
  </div>
</template>

<style scoped>
  /* These styles only apply to the current component */
  .component {
    border: 1px solid #eee;
  }
</style>

<script>
  export default {
    // Component logic
  }
</script>
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Front End Chuan, Chen Chuan's Code Teahouse 🍵, specializing in exorcising all kinds of stubborn bugs 💻. Daily serving baldness-warning-level development insights 🛠️, with a bonus of one-liners that'll make you laugh for ten years 🐟. Occasionally drops pixel-perfect romance brewed in a coffee cup ☕.

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