remark-kbd/src/index.js

This plugin parses custom Markdown syntax to handle keyboard keys. It adds a new node type to the [mdast][mdast] produced by [remark][remark]: `kbd`

const whitespace = require('is-whitespace-character')

const DEFAULT_LEFT = '|'
const DEFAULT_RIGHT = '|'

function plugin (config) {
  const CHAR_LEFT = (config && config.charLeft) || DEFAULT_LEFT
  const CHAR_RIGHT = (config && config.charRight) || DEFAULT_RIGHT

  const DOUBLE_LEFT = CHAR_LEFT + CHAR_LEFT
  const DOUBLE_RIGHT = CHAR_RIGHT + CHAR_RIGHT

  function locator (value, fromIndex) {
    const index = value.indexOf(DOUBLE_LEFT, fromIndex)
    return index
  }

  function inlineTokenizer (eat, value, silent) {
    if (
      !this.options.gfm ||
      (value.substr(0, 2) !== DOUBLE_LEFT) ||
      (value.substr(0, 4) === (DOUBLE_LEFT + DOUBLE_RIGHT)) ||
      whitespace(value.charAt(2))
    ) {
      return
    }

    let character = ''
    let previous = ''
    let preceding = ''
    let subvalue = ''
    let index = 1
    const length = value.length
    const now = eat.now()
    now.column += 2
    now.offset += 2

    while (++index < length) {
      character = value.charAt(index)

      if (
        character === CHAR_RIGHT &&
        previous === CHAR_RIGHT &&
        (!preceding || !whitespace(preceding))
      ) {
        /* istanbul ignore if - never used (yet) */
        if (silent) return true

        return eat(DOUBLE_LEFT + subvalue + DOUBLE_RIGHT)({
          type: 'kbd',
          children: this.tokenizeInline(subvalue, now),
          data: {
            hName: 'kbd'
          }
        })
      }

      subvalue += previous
      preceding = previous
      previous = character
    }
  }

  inlineTokenizer.locator = locator

  const Parser = this.Parser

  // Inject inlineTokenizer
  const inlineTokenizers = Parser.prototype.inlineTokenizers
  const inlineMethods = Parser.prototype.inlineMethods
  inlineTokenizers.kbd = inlineTokenizer
  inlineMethods.splice(inlineMethods.indexOf('text'), 0, 'kbd')

  const Compiler = this.Compiler

  // Stringify
  if (Compiler) {
    const visitors = Compiler.prototype.visitors
    visitors.kbd = function (node) {
      return `${DOUBLE_LEFT}${this.all(node).join('')}${DOUBLE_RIGHT}`
    }
  }
}

module.exports = plugin