Rehype Plugin to Remove HTTP-Equiv Meta Elements

4.0.1 · active · verified Wed Apr 22

`rehype-remove-meta-http-equiv` is a rehype plugin designed to optimize HTML output by removing `<meta>` elements that possess the `http-equiv` attribute. Specifically, it targets `content-type` and `content-language` meta tags, which can often be set more efficiently through other means (e.g., `charset` attribute on `<meta>` or `lang` attribute on `<html>`). This package is part of the broader unified ecosystem, focusing on transforming HTML syntax trees (hast). Currently at version 4.0.1, this package, along with other rehype plugins, aligns with the modern JavaScript module system, being ESM-only and requiring Node.js 16 or newer for its operation. Its primary purpose is to help reduce the transfer size of HTML documents, contributing to faster page loads without altering the semantic meaning of the document when alternatives for setting charset or language are present.

Common errors

```
ERR_REQUIRE_ESM: require() of ES Module ... not supported. Instead change the require of index.js in ... to a dynamic import() call.
```
cause Attempting to import the ESM-only `rehype-remove-meta-http-equiv` package using CommonJS `require()` syntax.

fix Change your import statement from `const plugin = require('rehype-remove-meta-http-equiv')` to `import plugin from 'rehype-remove-meta-http-equiv'` and ensure your project is configured for ESM (e.g., by adding `"type": "module"` to `package.json`).
```
TypeError: unified is not a function
```
cause The `unified` package was not imported correctly, or an incompatible version is being used (e.g., an older CommonJS `require` of a new ESM `unified`).

fix Ensure `unified` is imported using `import { unified } from 'unified'` and that you are using a compatible version (unified@^13 for rehype v4.x plugins).
```
SyntaxError: Cannot use import statement outside a module
```
cause You are attempting to use an `import` statement for `rehype-remove-meta-http-equiv` in a file that is being treated as a CommonJS module.

fix Add `"type": "module"` to your `package.json` file or use the `.mjs` file extension for your module file to explicitly enable ESM.

Warnings

breaking This package is ESM-only since version 4. Attempting to use 'require()' will result in an 'ERR_REQUIRE_ESM' error.
Fix: Migrate your project to use ECMAScript Modules (ESM) syntax with 'import' statements, or ensure your environment supports ESM.
breaking Version 4.0.0 and above require Node.js 16 or newer. Older Node.js versions are not supported, leading to potential runtime errors or unexpected behavior.
Fix: Upgrade your Node.js runtime to version 16 or later.
gotcha As rehype processes HTML, untrusted input combined with improper use can lead to Cross-Site Scripting (XSS) vulnerabilities. This plugin removes meta tags but does not sanitize other HTML content.
Fix: Always use `rehype-sanitize` (e.g., `.use(rehypeSanitize)`) in your processing pipeline when dealing with untrusted HTML content to prevent XSS attacks.
breaking The `rehype` ecosystem, including this plugin's compatibility, relies on `unified` v13+ and `hast` v3+. Incompatible versions can cause type errors or runtime failures.
Fix: Update your `unified`, `rehype-parse`, and `rehype-stringify` packages to their latest major versions (e.g., `unified@^13`, `rehype-parse@^9`, `rehype-stringify@^10`) to ensure compatibility.

Install

npm install rehype-remove-meta-http-equiv npm
yarn add rehype-remove-meta-http-equiv yarn
pnpm add rehype-remove-meta-http-equiv pnpm

Imports

rehypeRemoveMetaHttpEquiv

wrong:

const rehypeRemoveMetaHttpEquiv = require('rehype-remove-meta-http-equiv')

correct:

import rehypeRemoveMetaHttpEquiv from 'rehype-remove-meta-http-equiv'

This package is ESM-only since v4. CommonJS 'require' is not supported.

rehypeRemoveMetaHttpEquiv (CLI config)
```
"plugins": ["rehype-remove-meta-http-equiv"]
```
When used in rehype CLI configuration (e.g., package.json or .rehyperc), refer to the plugin by its string name without explicit import.
rehypeRemoveMetaHttpEquiv (Type)
```
import type { VFile } from 'vfile'
```
While `rehypeRemoveMetaHttpEquiv` is a function, its usage within the `unified` ecosystem often involves `VFile` for input/output and processing messages. The plugin itself is typed, so TypeScript understands its function signature.

Quickstart

This example demonstrates how to use `rehype-remove-meta-http-equiv` within a unified processing pipeline to strip `http-equiv` meta tags from an HTML document, showing the transformation from input to optimized output.

import rehypeParse from 'rehype-parse';
import rehypeRemoveMetaHttpEquiv from 'rehype-remove-meta-http-equiv';
import rehypeStringify from 'rehype-stringify';
import {read} from 'to-vfile';
import {unified} from 'unified';
import {join} from 'node:path';
import {tmpdir} from 'node:os';
import {writeFile} from 'node:fs/promises';

async function processHtml() {
  const inputHtml = `<!doctype html>
<html lang="en-GB">
  <head>
    <meta charset="utf8">
    <meta http-equiv="content-type" content="text/html; charset=chinese">
    <meta http-equiv="content-language" content="en-US">
  </head>
  <body>
    <h1>Hello World</h1>
    <p>This is a test document to show meta http-equiv removal.</p>
  </body>
</html>`;

  // Create a temporary file to simulate reading from a file system
  const tempFilePath = join(tmpdir(), 'input.html');
  await writeFile(tempFilePath, inputHtml, 'utf8');

  const file = await unified()
    .use(rehypeParse, {fragment: false}) // Ensure full document parsing
    .use(rehypeRemoveMetaHttpEquiv)
    .use(rehypeStringify)
    .process(await read(tempFilePath));

  console.log('Original HTML:\n', inputHtml);
  console.log('\nProcessed HTML:\n', String(file));
  // Expected output will have the meta http-equiv tags removed.
}

processHtml().catch(console.error);

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