index.js

/*
  Module dependencies
*/
var ElementType = require('domelementtype');
var entities = require('entities');

/* mixed-case SVG and MathML tags & attributes
   recognized by the HTML parser, see
   https://html.spec.whatwg.org/multipage/parsing.html#parsing-main-inforeign
*/
var foreignNames = require('./foreignNames.json');
foreignNames.elementNames.__proto__ = null; /* use as a simple dictionary */
foreignNames.attributeNames.__proto__ = null;

var unencodedElements = {
  __proto__: null,
  style: true,
  script: true,
  xmp: true,
  iframe: true,
  noembed: true,
  noframes: true,
  plaintext: true,
  noscript: true
};

/*
  Format attributes
*/
function formatAttrs(attributes, opts) {
  if (!attributes) return;

  var output = '';
  var value;

  // Loop through the attributes
  for (var key in attributes) {
    value = attributes[key];
    if (output) {
      output += ' ';
    }

    if (opts.xmlMode === 'foreign') {
      /* fix up mixed-case attribute names */
      key = foreignNames.attributeNames[key] || key;
    }
    output += key;
    if ((value !== null && value !== '') || opts.xmlMode) {
      output +=
        '="' +
        (opts.decodeEntities
          ? entities.encodeXML(value)
          : value.replace(/\"/g, '"')) +
        '"';
    }
  }

  return output;
}

/*
  Self-enclosing tags (stolen from node-htmlparser)
*/
var singleTag = {
  __proto__: null,
  area: true,
  base: true,
  basefont: true,
  br: true,
  col: true,
  command: true,
  embed: true,
  frame: true,
  hr: true,
  img: true,
  input: true,
  isindex: true,
  keygen: true,
  link: true,
  meta: true,
  param: true,
  source: true,
  track: true,
  wbr: true
};

var render = (module.exports = function(dom, opts) {
  if (!Array.isArray(dom) && !dom.cheerio) dom = [dom];
  opts = opts || {};

  var output = '';

  for (var i = 0; i < dom.length; i++) {
    var elem = dom[i];

    if (elem.type === 'root') output += render(elem.children, opts);
    else if (ElementType.isTag(elem)) output += renderTag(elem, opts);
    else if (elem.type === ElementType.Directive)
      output += renderDirective(elem);
    else if (elem.type === ElementType.Comment) output += renderComment(elem);
    else if (elem.type === ElementType.CDATA) output += renderCdata(elem);
    else output += renderText(elem, opts);
  }

  return output;
});

var foreignModeIntegrationPoints = [
  'mi',
  'mo',
  'mn',
  'ms',
  'mtext',
  'annotation-xml',
  'foreignObject',
  'desc',
  'title'
];

function renderTag(elem, opts) {
  // Handle SVG / MathML in HTML
  if (opts.xmlMode === 'foreign') {
    /* fix up mixed-case element names */
    elem.name = foreignNames.elementNames[elem.name] || elem.name;
    /* exit foreign mode at integration points */
    if (
      elem.parent &&
      foreignModeIntegrationPoints.indexOf(elem.parent.name) >= 0
    )
      opts = Object.assign({}, opts, { xmlMode: false });
  }
  if (!opts.xmlMode && ['svg', 'math'].indexOf(elem.name) >= 0) {
    opts = Object.assign({}, opts, { xmlMode: 'foreign' });
  }

  var tag = '<' + elem.name;
  var attribs = formatAttrs(elem.attribs, opts);

  if (attribs) {
    tag += ' ' + attribs;
  }

  if (opts.xmlMode && (!elem.children || elem.children.length === 0)) {
    tag += '/>';
  } else {
    tag += '>';
    if (elem.children) {
      tag += render(elem.children, opts);
    }

    if (!singleTag[elem.name] || opts.xmlMode) {
      tag += '</' + elem.name + '>';
    }
  }

  return tag;
}

function renderDirective(elem) {
  return '<' + elem.data + '>';
}

function renderText(elem, opts) {
  var data = elem.data || '';

  // if entities weren't decoded, no need to encode them back
  if (
    opts.decodeEntities &&
    !(elem.parent && elem.parent.name in unencodedElements)
  ) {
    data = entities.encodeXML(data);
  }

  return data;
}

function renderCdata(elem) {
  return '<![CDATA[' + elem.children[0].data + ']]>';
}

function renderComment(elem) {
  return '<!--' + elem.data + '-->';
}