Run code blocks in your markdown and annotate them with the output.

Creating README files is a pain, especially when it comes to writing code samples. Code gets out of date, authors get sloppy, details get omitted, etc. RunMD takes the pain out of this process.

With RunMD, your readers can trust your code blocks are runnable and that code output will be as-claimed.

Install

npm install runmd

Usage

runmd [options] input_file

Where options may be zero or more of:

• --output=output_file file to write specify an output file
• --watch Watch input_file for changes and rerender
• --lame Suppress attribution footer

For example, to port an existing README.md file:

cp README.md README_js.md

Edit README_js.md to add Markdown Options (below) to your ````javascript` blocks, then ...

runmd README_js.md --output README.md

Limitations

RunMD scripts are run using Node.js' vm module. This environment is limited in "interesting" ways, and RunMD runs fast and loose with some APIs. Specifically:

• console.log() works, but no other console methods are supported at this time
• setTimeout() works, but all timers fire immediately at the end of script execution. clearTimeout, setInterval, and clearInterval are not supported

[Note: PRs fleshing out these and other missing APIs would be "well received"]

ES6 Imports

Some ES6 import incantations will work, however this feature should be considered very experimental at this point. Read the source for details.

NPM Integration

To avoid publishing when compilation of your README file fails:

"scripts": {
  "prepare": "runmd README_js.md --output README.md"
}

Markdown API

--run

Runs the script, appending any console.log output. E.g.:

```javascript --run
console.log('Hello, World!');
```

... becomes:

```javascript
console.log('Hello, World!');

⇒ Hello, World!
````

--run may be omitted if other options are present.

--run [context_name]

If a context_name is provided, all blocks with that name will share the same runtime context. E.g.

```javascript --run sample
let text = 'World';
```

Continuing on ...

```javascript --run sample
console.log(text);
```

... becomes:

```javascript
let text = 'Hello';
```

Continuing on ...

```javascript
console.log(text);

⇒ Hello
```

... but trying to reference text in a new context or other named context will fail:

```javascript --run
console.log(text);
```

(Results in ReferenceError: text is not defined.)

--hide

Run the script, but do not render the script source or output. This is useful for setting up context that's necessary for code, but not germane to documentation.

Welcome!

```javascript --run foo --hide
// Setup/utility code or whatever ...
function hello() {
  console.log('Hello, World!');
}
```

Here is a code snippet:

```javascript --run foo
hello();
```

... becomes:

Welcome!

Here's a code snippet:

```javascript
hello();

⇒ Hello, World!
```

"// RESULT"

Inline values for single line expressions may be displayed by appending "// RESULT" to the end of a line. Note: RunMD will error if the line is not a self-contained, evaluate-able, expression.

```javascript --run
['Hello', ' World!'].join(','); // RESULT
```

... becomes:

```javascript
['Hello', ' World!'].join(','); // ⇨ 'Hello, World!'
```

runmd Object

A global runmd object is provided all contexts, and supports the following:

runmd.onRequire

The onRequire event gives pages the opportunity to transform module require paths. This is useful if the module context in which you render markdown is different from what your readers will typically encounter. (Often the case with npm-published modules).

```javascript --hide
// Remap `require('uuid/*') to `require('./*')
runmd.onRequire = function(path) {
  return path.replace(/^uuid\//, './');
}
```

runmd.onOutputLine

The onOutputLine event gives pages the opportunity to transform markdown output.

```javascript --hide
runmd.onOutputLine = function(line, isRunning) {
  return !isRunning ? line.toUpperCase() : line);
}
```

The isRunning argument will be true for any lines that are interpreted as code by this module. Transformations do not affect interpreted source, only how source is rendered.

Return null to omit the line from the rendered output.

Recommended workflow: RunMD + Chrome + Markdown Preview Plus

There's more than one way to visualize changes to Markdown files as you edit them, but the following works pretty well for me:

• Install the Markdown Preview Plus Chrome
• ... Allow it to access file URLs" (in chrome://extensions tab)
• ... Set Reload Frequency to "1 second" (in the extension options)
• Launch runmd with the --watch option to have it continuously re-render your output file as you make changes
• Open the output file in Chrome, and it will update in realtime as you make changes to your runmd input file(s)

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Markdown generated from src/README_js.md by