eslint-plugin-markdown-preferences

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markdown-preferences/prefer-fenced-code-blocks ​

enforce the use of fenced code blocks over indented code blocks

  • ⚙️ This rule is included in plugin.configs.recommended.
  • 🔧 The --fix option on the command line can automatically fix some of the problems reported by this rule.

📖 Rule Details ​

This rule enforces the use of fenced code blocks (using three backticks ```` or tildes ~~~) instead of indented code blocks (using four spaces or a tab) in Markdown files.

Why use fenced code blocks?

  • Fenced code blocks are easier to read and maintain, especially in documents with mixed content or nested structures.
  • They allow you to specify the programming language for syntax highlighting (e.g., ```js), improving code clarity.
  • Fenced code blocks are supported consistently across modern Markdown parsers, while indented code blocks can be ambiguous or misinterpreted, especially inside blockquotes or lists.
  • Indented code blocks can be confused with nested content or list items, leading to readability and rendering issues.

Autofix behavior

This rule can automatically convert simple indented code blocks to fenced code blocks. However, autofix is not applied if:

  • The indentation is inconsistent across lines.
  • The code block mixes tabs and spaces in the indentation, which can be ambiguous and unsafe to convert automatically.

Practical notes

  • Both backtick (```) and tilde (~~~) fences are allowed.
  • A language specifier is not required, but recommended for syntax highlighting.
  • Indented code blocks inside blockquotes or lists are also targeted by this rule.
md
<!-- eslint markdown-preferences/prefer-fenced-code-blocks: 'error' -->

<!-- ✓ GOOD -->

```js
function foo() {
  return 42;
}
```

```js
function bar() {
  return 99;
}
```

<!-- ✗ BAD -->


    function foo() {

      return 42;
    }

> 
    // code in blockquote

>     function foo() {
>       return 42;
>     }

🔧 Options ​

This rule does not accept any options.

📚 Further Reading ​

🚀 Version ​

This rule was introduced in eslint-plugin-markdown-preferences v0.11.0

🔍 Implementation ​