markdown-it-named-headings/index.js

Add IDs to heading elements in markdown-it

var kebabcase = require('lodash.kebabcase')
var unidecode = require('unidecode')

module.exports = function plugin (md, options) {
  md.core.ruler.push('named_headings', namedHeadings.bind(null, md))
}

function namedHeadings (md, state) {
  var ids = {}

  state.tokens.forEach(function (token, i) {
    if (token.type === 'heading_open') {
      var text = md.renderer.render(state.tokens[i + 1].children, md.options)
      var id = kebabcase(unidecode(text))
      var uniqId = uncollide(ids, id)
      ids[uniqId] = true
      setAttr(token, 'id', uniqId)
    }
  })
}

function uncollide (ids, id) {
  if (!ids[id]) return id
  var i = 1
  while (ids[id + '-' + i]) { i++ }
  return id + '-' + i
}

function setAttr (token, attr, value, options) {
  var idx = token.attrIndex(attr)

  if (idx === -1) {
    token.attrPush([ attr, value ])
  } else if (options && options.append) {
    token.attrs[idx][1] =
      token.attrs[idx][1] + ' ' + value
  } else {
    token.attrs[idx][1] = value
  }
}