HTML文本框左侧动态行号技巧

HTML 在 textarea 左侧添加行号的实现方法

在文本编辑器中显示行号是提升用户体验的常见需求。以下介绍几种在 <textarea> 左侧动态添加行号的实现方案，涵盖纯 HTML/CSS 和 JavaScript 动态生成的方法。

使用 CSS 和 JavaScript 动态生成行号

通过创建一个行号容器与 <textarea> 联动滚动，实现行号同步更新。

<div class="code-editor">
  <div class="line-numbers"></div>
  <textarea id="code"></textarea>
</div>

.code-editor {
  display: flex;
  font-family: monospace;
}
.line-numbers {
  padding: 10px;
  text-align: right;
  background: #f5f5f5;
  margin-right: 5px;
  overflow-y: hidden;
}
textarea {
  flex: 1;
  padding: 10px;
  border: 1px solid #ddd;
  min-height: 200px;
  line-height: 1.5;
}

const textarea = document.getElementById('code');
const lineNumbers = document.querySelector('.line-numbers');

textarea.addEventListener('input', updateLineNumbers);
textarea.addEventListener('scroll', syncScroll);

function updateLineNumbers() {
  const lines = textarea.value.split('\n').length;
  lineNumbers.innerHTML = Array(lines).fill('<span></span>').map((_, i) => `<span>${i + 1}</span>`).join('<br>');
}

function syncScroll() {
  lineNumbers.scrollTop = textarea.scrollTop;
}

updateLineNumbers(); // 初始化

利用 contenteditable 模拟编辑器

通过 <div contenteditable> 替代 <textarea> 实现更复杂的行号样式。

<div class="editor">
  <div class="gutter"></div>
  <div class="content" contenteditable></div>
</div>

document.querySelector('.content').addEventListener('input', function() {
  const lines = this.textContent.split('\n').length;
  document.querySelector('.gutter').innerHTML = 
    Array(lines).fill().map((_, i) => i + 1).join('<br>');
});

使用第三方库快速实现

对于复杂需求，可考虑现成库如：

• CodeMirror: 支持行号、语法高亮等专业功能
• PrismJS: 轻量级代码高亮工具
• Ace Editor: 云端代码编辑器解决方案

// CodeMirror 示例
const editor = CodeMirror.fromTextArea(document.getElementById('code'), {
  lineNumbers: true,
  mode: 'htmlmixed'
});

关键注意事项

• 性能优化: 对于大文件需使用虚拟滚动技术
• 行高同步: 确保行号与文本的行高一致
• 移动端适配: 触控事件需特殊处理
• 无障碍访问: 为行号添加 ARIA 属性

以上方案可根据项目需求选择简单实现或专业编辑器集成，平衡功能与复杂度。

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