markdown-it-mathjax.js

;(function (root, factory) {
  if (typeof exports === 'object') {
    module.exports = factory()
  } else {
    root.markdownitMathjax = factory()
  }
})(this, function () {
  function math (state, silent) {
    var startMathPos = state.pos
    if (state.src.charCodeAt(startMathPos) !== 0x5C /* \ */) {
      return false
    }
    var match = state.src.slice(++startMathPos).match(/^(?:\\\[|\\\(|begin\{([^}]*)\})/)
    if (!match) {
      return false
    }
    startMathPos += match[0].length
    var type, endMarker, includeMarkers
    if (match[0] === '\\[') {
      type = 'display_math'
      endMarker = '\\\\]'
    } else if (match[0] === '\\(') {
      type = 'inline_math'
      endMarker = '\\\\)'
    } else if (match[1]) {
      type = 'math'
      endMarker = '\\end{' + match[1] + '}'
      includeMarkers = true
    }
    var endMarkerPos = state.src.indexOf(endMarker, startMathPos)
    if (endMarkerPos === -1) {
      return false
    }
    var nextPos = endMarkerPos + endMarker.length
    if (!silent) {
      var token = state.push(type, '', 0)
      token.content = includeMarkers
        ? state.src.slice(state.pos, nextPos)
        : state.src.slice(startMathPos, endMarkerPos)
    }
    state.pos = nextPos
    return true
  }

  function texMath (state, silent) {
    var startMathPos = state.pos
    if (state.src.charCodeAt(startMathPos) !== 0x24 /* $ */) {
      return false
    }

    // Parse tex math according to http://pandoc.org/README.html#math
    var endMarker = '$'
    var afterStartMarker = state.src.charCodeAt(++startMathPos)
    if (afterStartMarker === 0x24 /* $ */) {
      endMarker = '$$'
      if (state.src.charCodeAt(++startMathPos) === 0x24 /* $ */) {
        // 3 markers are too much
        return false
      }
    } else {
      // Skip if opening $ is succeeded by a space character
      if (afterStartMarker === 0x20 /* space */ || afterStartMarker === 0x09 /* \t */ || afterStartMarker === 0x0a /* \n */) {
        return false
      }
    }
    var endMarkerPos = state.src.indexOf(endMarker, startMathPos)
    if (endMarkerPos === -1) {
      return false
    }
    if (state.src.charCodeAt(endMarkerPos - 1) === 0x5C /* \ */) {
      return false
    }
    var nextPos = endMarkerPos + endMarker.length
    if (endMarker.length === 1) {
      // Skip if $ is preceded by a space character
      var beforeEndMarker = state.src.charCodeAt(endMarkerPos - 1)
      if (beforeEndMarker === 0x20 /* space */ || beforeEndMarker === 0x09 /* \t */ || beforeEndMarker === 0x0a /* \n */) {
        return false
      }
      // Skip if closing $ is succeeded by a digit (eg $5 $10 ...)
      var suffix = state.src.charCodeAt(nextPos)
      if (suffix >= 0x30 && suffix < 0x3A) {
        return false
      }
    }

    if (!silent) {
      var token = state.push(endMarker.length === 1 ? 'inline_math' : 'display_math', '', 0)
      token.content = state.src.slice(startMathPos, endMarkerPos)
    }
    state.pos = nextPos
    return true
  }

  function escapeHtml (html) {
    return html.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/\u00a0/g, ' ')
  }

  function extend (options, defaults) {
    return Object.keys(defaults).reduce(function (result, key) {
      if (result[key] === undefined) {
        result[key] = defaults[key]
      }
      return result
    }, options)
  }

  var mapping = {
    'math': 'Math',
    'inline_math': 'InlineMath',
    'display_math': 'DisplayMath'
  }

  return function (options) {
    var defaults = {
      beforeMath: '',
      afterMath: '',
      beforeInlineMath: '\\(',
      afterInlineMath: '\\)',
      beforeDisplayMath: '\\[',
      afterDisplayMath: '\\]'
    }
    options = extend(options || {}, defaults)

    return function (md) {
      md.inline.ruler.before('escape', 'math', math)
      md.inline.ruler.push('texMath', texMath)

      Object.keys(mapping).forEach(function (key) {
        var before = options['before' + mapping[key]]
        var after = options['after' + mapping[key]]
        md.renderer.rules[key] = function (tokens, idx) {
          return before + escapeHtml(tokens[idx].content) + after
        }
      })
    }
  }
})