RunMD

Run and annotate JS or TS code blocks in MarkDown files!

Note: Version 2 is a bit of a reset for this project as far as how things are implemented. As of runmd@2 CommonJS is no longer supported and and code is expected to use ESM. Also, node@22+ is required.

Install

npm install runmd

Quick Start

1. Make a copy of your existing README. E.g. cp README.md README_js.md
2. Edit README_js.md and add the --run flag to any ```javascript blocks you'd like processed
3. Add // RESULT or console.log() to add runtime state
4. Run it with runmd README_js.md --output README.md

Usage

$ runmd --help
Usage: runmd [options] <input_file>

Arguments:
  input_file           markdown file to process

Options:
  -o, --output <file>  output file
  --check              verify output file is up to date, exit 1 if not
  --no-footer          omit the runmd footer
  -w, --watch          watch for changes
  -h, --help           display help for command

Markdown API

--run option

Add --run to any JS or TS code block ( ```js, ```ts, ```javascript, ```typescript) to enable runmd processing. E.g.:

```javascript --run
`Hello, ${'Fred Smith'}!`; // RESULT
```

... becomes:

```javascript --run
`Hello, ${'Fred Smith'}!`; // ⇨ 'Fred Smith!'
```

--hide option

To remove a block from output, add the --hide option. For example:

```javascript --hide
`... this block is removed from output`;
```

// RESULT

Add // RESULT after an expression to document it's value.

For example:

```javascript --run
const a = 'Hello'; // RESULT
a + ', world!'; // RESULT
```

... becomes:

```javascript
const a = "Hello"; // ⇨ 'Hello'
a + ", world!"; // ⇨ 'Hello, world!'
```

[!Note]

The code in question must be self-contained on a single line. Multi-line expressions are not supported.

console.log

Use console.log(...) to document one or more runtime values.

For example:

```javascript --run
const item = { id: 42, tags: ['a', 'b'] };
console.log(item);
```

... becomes:

```javascript --run
const item = { id: 42, tags: ['a', 'b'] };
console.log(item);
// ⇨ { id: 42, tags: [ 'a', 'b' ] }
```

[!Note]

Like // RESULT, console.log() must be self-contained on a single line.

Other console APIs (error(), warn(), info(), etc.) are not supported and will error.

Loops

If multiple passes are made over a line with // RESULT or console.log(), all values will be shown in the order they were produced.

For example:

```javascript --run
for (const word of 'The quick brown fox'.split(' ')) {
  word.toUpperCase(); //  RESULT
  console.log(word.match(/[aeiou]/g))
}
```

... becomes:

```javascript --run
for (const [_, word] in 'works for me'.split(' ')) {
  word.toUpperCase(); // ⇨ 'THE'
  // ⇨ 'QUICK'
  // ⇨ 'BROWN'
  // ⇨ 'FOX'
  console.log(word.match(/[aeiou]/g));
  // ⇨ [ 'e' ]
  // ⇨ [ 'u', 'i' ]
  // ⇨ [ 'o' ]
  // ⇨ [ 'o' ]
}
```

Types of blocks

runmd distinguishes between --run'able blocks as follows:

• Setup block - A block that references the runmd global
• Module block - A block that uses ESM import or export directives
• Simple block - Any other block

(Note that a Setup block can also be a Module block)

Simple block context sharing

Simple blocks run in the same context as any preceding block. For example:

```javascript --run
const foo = 'Hello';
```

```javascript --run
foo + ', world!'; // `foo` is [still] defined
```

Module block context sharing

The context resets when a Setup block is encountered. The Setup block is run as part of setting up the new context.

The context also resets when a Module block is encountered. runmd will run the most recently encountered Setup block, then run the Module block. For example:

globalThis["run" + "md"]; // ⇨ { importMap: { imports: {} } }
const foo = 123;
// Simple block - we have access to previous block state
foo + 321; // ⇨ 444

runmd;

import "node:path"; // "import" here makes this a Module block

export default {}; //

Setup block context sharing

runmd.importMap

runmd has basic support for import maps in the form of runmd.importMap.imports. For example:

```javascript --run
runmd.importMap = {
  imports: {
    'foo': './src/foo.ts'
  }
}
```

```javascript --run
import foo from 'foo';  // Imports './src/foo.ts'
```

runmd.onOutputLine

The runmd.onOutputLine callback can be used to transform the generated markdown.

For example:

```javascript --run
/**
 * @param {string} line Output line text.
 * @param {object|undefined} inBlock Current code block, if this line came from one.
 * @returns {string|undefined} Return undefined to drop the line, or a string to keep/replace it.
 */
runmd.onOutputLine = (line, inBlock) => {
  if (line === '```javascript' || line === '```') {
    return undefined; // Drop code fence lines
  }

  if (!inBlock && line.startsWith('# ')) {
    return line.toUpperCase(); // Rewrite markdown headings
  }

  return line;
};
```

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Generated from README_js.md by runmd