front-matter/index.js

Extract YAML front matter from a string

var parser = require('js-yaml')
var optionalByteOrderMark = '\\ufeff?'
var pattern = '^('
      + optionalByteOrderMark
      + '(= yaml =|---)'
      + '$([\\s\\S]*?)'
      + '\\2'
      + '$'
      + (process.platform === 'win32' ? '\\r?' : '')
      + '(?:\\n)?)'
// NOTE: If this pattern uses the 'g' flag the `regex` variable definition will
// need to be moved down into the functions that use it.
var regex = new RegExp(pattern, 'm')

module.exports = extractor
module.exports.test = test

function extractor(string) {
  string = string || ''

  var lines = string.split(/(\r?\n)/)
  if (lines[0] && /= yaml =|---/.test(lines[0])) {
    return parse(string)
  } else {
    return { attributes: {}, body: string }
  }
}

function parse(string) {
  var match = regex.exec(string)

  if (! match) {
    return {
      attributes: {},
      body: string
    }
  }

  var yaml = match[match.length - 1].replace(/^\s+|\s+$/g, '')
  var attributes = parser.load(yaml) || {}
  var body = string.replace(match[0], '')

  return { attributes: attributes, body: body }
}

function test(string){
  string = string || ''

  return regex.test(string)
}