turndown.js

var TurndownService = (function () {
  "use strict";

  function extend(destination) {
    for (var i = 1; i < arguments.length; i++) {
      var source = arguments[i];
      for (var key in source) {
        if (source.hasOwnProperty(key)) destination[key] = source[key];
      }
    }
    return destination;
  }

  function repeat(character, count) {
    return Array(count + 1).join(character);
  }

  function trimLeadingNewlines(string) {
    return string.replace(/^\n*/, "");
  }

  function trimTrailingNewlines(string) {
    // avoid match-at-end regexp bottleneck, see #370
    var indexEnd = string.length;
    while (indexEnd > 0 && string[indexEnd - 1] === "\n") indexEnd--;
    return string.substring(0, indexEnd);
  }

  var blockElements = [
    "ADDRESS",
    "ARTICLE",
    "ASIDE",
    "AUDIO",
    "BLOCKQUOTE",
    "BODY",
    "CANVAS",
    "CENTER",
    "DD",
    "DIR",
    "DIV",
    "DL",
    "DT",
    "FIELDSET",
    "FIGCAPTION",
    "FIGURE",
    "FOOTER",
    "FORM",
    "FRAMESET",
    "H1",
    "H2",
    "H3",
    "H4",
    "H5",
    "H6",
    "HEADER",
    "HGROUP",
    "HR",
    "HTML",
    "ISINDEX",
    "LI",
    "MAIN",
    "MENU",
    "NAV",
    "NOFRAMES",
    "NOSCRIPT",
    "OL",
    "OUTPUT",
    "P",
    "PRE",
    "SECTION",
    "TABLE",
    "TBODY",
    "TD",
    "TFOOT",
    "TH",
    "THEAD",
    "TR",
    "UL",
  ];

  function isBlock(node) {
    return is(node, blockElements);
  }

  var voidElements = [
    "AREA",
    "BASE",
    "BR",
    "COL",
    "COMMAND",
    "EMBED",
    "HR",
    "IMG",
    "INPUT",
    "KEYGEN",
    "LINK",
    "META",
    "PARAM",
    "SOURCE",
    "TRACK",
    "WBR",
  ];

  function isVoid(node) {
    return is(node, voidElements);
  }

  function hasVoid(node) {
    return has(node, voidElements);
  }

  var meaningfulWhenBlankElements = ["A", "TABLE", "THEAD", "TBODY", "TFOOT", "TH", "TD", "IFRAME", "SCRIPT", "AUDIO", "VIDEO"];

  function isMeaningfulWhenBlank(node) {
    return is(node, meaningfulWhenBlankElements);
  }

  function hasMeaningfulWhenBlank(node) {
    return has(node, meaningfulWhenBlankElements);
  }

  function is(node, tagNames) {
    return tagNames.indexOf(node.nodeName) >= 0;
  }

  function has(node, tagNames) {
    return (
      node.getElementsByTagName &&
      tagNames.some(function (tagName) {
        return node.getElementsByTagName(tagName).length;
      })
    );
  }

  var rules = {};

  rules.paragraph = {
    filter: "p",

    replacement: function (content) {
      return "\n\n" + content + "\n\n";
    },
  };

  rules.lineBreak = {
    filter: "br",

    replacement: function (content, node, options) {
      return options.br + "\n";
    },
  };

  rules.heading = {
    filter: ["h1", "h2", "h3", "h4", "h5", "h6"],

    replacement: function (content, node, options) {
      var hLevel = Number(node.nodeName.charAt(1));

      if (options.headingStyle === "setext" && hLevel < 3) {
        var underline = repeat(hLevel === 1 ? "=" : "-", content.length);
        return "\n\n" + content + "\n" + underline + "\n\n";
      } else {
        return "\n\n" + repeat("#", hLevel) + " " + content + "\n\n";
      }
    },
  };

  rules.blockquote = {
    filter: "blockquote",

    replacement: function (content) {
      content = content.replace(/^\n+|\n+$/g, "");
      content = content.replace(/^/gm, "> ");
      return "\n\n" + content + "\n\n";
    },
  };

  rules.list = {
    filter: ["ul", "ol"],

    replacement: function (content, node) {
      var parent = node.parentNode;
      if (parent.nodeName === "LI" && parent.lastElementChild === node) {
        return "\n" + content;
      } else {
        return "\n\n" + content + "\n\n";
      }
    },
  };

  rules.listItem = {
    filter: "li",

    replacement: function (content, node, options) {
      content = content
        .replace(/^\n+/, "") // remove leading newlines
        .replace(/\n+$/, "\n") // replace trailing newlines with just a single one
        .replace(/\n/gm, "\n    "); // indent
      var prefix = options.bulletListMarker + "   ";
      var parent = node.parentNode;
      if (parent.nodeName === "OL") {
        var start = parent.getAttribute("start");
        var index = Array.prototype.indexOf.call(parent.children, node);
        prefix = (start ? Number(start) + index : index + 1) + ".  ";
      }
      return prefix + content + (node.nextSibling && !/\n$/.test(content) ? "\n" : "");
    },
  };

  rules.indentedCodeBlock = {
    filter: function (node, options) {
      return options.codeBlockStyle === "indented" && node.nodeName === "PRE" && node.firstChild && node.firstChild.nodeName === "CODE";
    },

    replacement: function (content, node, options) {
      return "\n\n    " + node.firstChild.textContent.replace(/\n/g, "\n    ") + "\n\n";
    },
  };

  rules.fencedCodeBlock = {
    filter: function (node, options) {
      return options.codeBlockStyle === "fenced" && node.nodeName === "PRE" && node.firstChild && node.firstChild.nodeName === "CODE";
    },

    replacement: function (content, node, options) {
      var className = node.firstChild.getAttribute("class") || "";
      var language = (className.match(/language-(\S+)/) || [null, ""])[1];
      var code = node.firstChild.textContent;

      var fenceChar = options.fence.charAt(0);
      var fenceSize = 3;
      var fenceInCodeRegex = new RegExp("^" + fenceChar + "{3,}", "gm");

      var match;
      while ((match = fenceInCodeRegex.exec(code))) {
        if (match[0].length >= fenceSize) {
          fenceSize = match[0].length + 1;
        }
      }

      var fence = repeat(fenceChar, fenceSize);

      return "\n\n" + fence + language + "\n" + code.replace(/\n$/, "") + "\n" + fence + "\n\n";
    },
  };

  rules.horizontalRule = {
    filter: "hr",

    replacement: function (content, node, options) {
      return "\n\n" + options.hr + "\n\n";
    },
  };

  rules.inlineLink = {
    filter: function (node, options) {
      return options.linkStyle === "inlined" && node.nodeName === "A" && node.getAttribute("href");
    },

    replacement: function (content, node) {
      var href = node.getAttribute("href");
      if (href) href = href.replace(/([()])/g, "\\$1");
      var title = cleanAttribute(node.getAttribute("title"));
      if (title) title = ' "' + title.replace(/"/g, '\\"') + '"';
      return "[" + content + "](" + href + title + ")";
    },
  };

  rules.referenceLink = {
    filter: function (node, options) {
      return options.linkStyle === "referenced" && node.nodeName === "A" && node.getAttribute("href");
    },

    replacement: function (content, node, options) {
      var href = node.getAttribute("href");
      var title = cleanAttribute(node.getAttribute("title"));
      if (title) title = ' "' + title + '"';
      var replacement;
      var reference;

      switch (options.linkReferenceStyle) {
        case "collapsed":
          replacement = "[" + content + "][]";
          reference = "[" + content + "]: " + href + title;
          break;
        case "shortcut":
          replacement = "[" + content + "]";
          reference = "[" + content + "]: " + href + title;
          break;
        default:
          var id = this.references.length + 1;
          replacement = "[" + content + "][" + id + "]";
          reference = "[" + id + "]: " + href + title;
      }

      this.references.push(reference);
      return replacement;
    },

    references: [],

    append: function (options) {
      var references = "";
      if (this.references.length) {
        references = "\n\n" + this.references.join("\n") + "\n\n";
        this.references = []; // Reset references
      }
      return references;
    },
  };

  rules.emphasis = {
    filter: ["em", "i"],

    replacement: function (content, node, options) {
      if (!content.trim()) return "";
      return options.emDelimiter + content + options.emDelimiter;
    },
  };

  rules.strong = {
    filter: ["strong", "b"],

    replacement: function (content, node, options) {
      if (!content.trim()) return "";
      return options.strongDelimiter + content + options.strongDelimiter;
    },
  };

  rules.code = {
    filter: function (node) {
      var hasSiblings = node.previousSibling || node.nextSibling;
      var isCodeBlock = node.parentNode.nodeName === "PRE" && !hasSiblings;

      return node.nodeName === "CODE" && !isCodeBlock;
    },

    replacement: function (content) {
      if (!content) return "";
      content = content.replace(/\r?\n|\r/g, " ");

      var extraSpace = /^`|^ .*?[^ ].* $|`$/.test(content) ? " " : "";
      var delimiter = "`";
      var matches = content.match(/`+/gm) || [];
      while (matches.indexOf(delimiter) !== -1) delimiter = delimiter + "`";

      return delimiter + extraSpace + content + extraSpace + delimiter;
    },
  };

  rules.image = {
    filter: "img",

    replacement: function (content, node) {
      var alt = cleanAttribute(node.getAttribute("alt"));
      var src = node.getAttribute("src") || "";
      var title = cleanAttribute(node.getAttribute("title"));
      var titlePart = title ? ' "' + title + '"' : "";
      return src ? "![" + alt + "]" + "(" + src + titlePart + ")" : "";
    },
  };

  function cleanAttribute(attribute) {
    return attribute ? attribute.replace(/(\n+\s*)+/g, "\n") : "";
  }

  /**
   * Manages a collection of rules used to convert HTML to Markdown
   */

  function Rules(options) {
    this.options = options;
    this._keep = [];
    this._remove = [];

    this.blankRule = {
      replacement: options.blankReplacement,
    };

    this.keepReplacement = options.keepReplacement;

    this.defaultRule = {
      replacement: options.defaultReplacement,
    };

    this.array = [];
    for (var key in options.rules) this.array.push(options.rules[key]);
  }

  Rules.prototype = {
    add: function (key, rule) {
      this.array.unshift(rule);
    },

    keep: function (filter) {
      this._keep.unshift({
        filter: filter,
        replacement: this.keepReplacement,
      });
    },

    remove: function (filter) {
      this._remove.unshift({
        filter: filter,
        replacement: function () {
          return "";
        },
      });
    },

    forNode: function (node) {
      if (node.isBlank) return this.blankRule;
      var rule;

      if ((rule = findRule(this.array, node, this.options))) return rule;
      if ((rule = findRule(this._keep, node, this.options))) return rule;
      if ((rule = findRule(this._remove, node, this.options))) return rule;

      return this.defaultRule;
    },

    forEach: function (fn) {
      for (var i = 0; i < this.array.length; i++) fn(this.array[i], i);
    },
  };

  function findRule(rules, node, options) {
    for (var i = 0; i < rules.length; i++) {
      var rule = rules[i];
      if (filterValue(rule, node, options)) return rule;
    }
    return void 0;
  }

  function filterValue(rule, node, options) {
    var filter = rule.filter;
    if (typeof filter === "string") {
      if (filter === node.nodeName.toLowerCase()) return true;
    } else if (Array.isArray(filter)) {
      if (filter.indexOf(node.nodeName.toLowerCase()) > -1) return true;
    } else if (typeof filter === "function") {
      if (filter.call(rule, node, options)) return true;
    } else {
      throw new TypeError("`filter` needs to be a string, array, or function");
    }
  }

  /**
   * The collapseWhitespace function is adapted from collapse-whitespace
   * by Luc Thevenard.
   *
   * The MIT License (MIT)
   *
   * Copyright (c) 2014 Luc Thevenard <lucthevenard@gmail.com>
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this software and associated documentation files (the "Software"), to deal
   * in the Software without restriction, including without limitation the rights
   * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   * copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in
   * all copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
   * THE SOFTWARE.
   */

  /**
   * collapseWhitespace(options) removes extraneous whitespace from an the given element.
   *
   * @param {Object} options
   */
  function collapseWhitespace(options) {
    var element = options.element;
    var isBlock = options.isBlock;
    var isVoid = options.isVoid;
    var isPre =
      options.isPre ||
      function (node) {
        return node.nodeName === "PRE";
      };

    if (!element.firstChild || isPre(element)) return;

    var prevText = null;
    var keepLeadingWs = false;

    var prev = null;
    var node = next(prev, element, isPre);

    while (node !== element) {
      if (node.nodeType === 3 || node.nodeType === 4) {
        // Node.TEXT_NODE or Node.CDATA_SECTION_NODE
        var text = node.data.replace(/[ \r\n\t]+/g, " ");

        if ((!prevText || / $/.test(prevText.data)) && !keepLeadingWs && text[0] === " ") {
          text = text.substr(1);
        }

        // `text` might be empty at this point.
        if (!text) {
          node = remove(node);
          continue;
        }

        node.data = text;

        prevText = node;
      } else if (node.nodeType === 1) {
        // Node.ELEMENT_NODE
        if (isBlock(node) || node.nodeName === "BR") {
          if (prevText) {
            prevText.data = prevText.data.replace(/ $/, "");
          }

          prevText = null;
          keepLeadingWs = false;
        } else if (isVoid(node) || isPre(node)) {
          // Avoid trimming space around non-block, non-BR void elements and inline PRE.
          prevText = null;
          keepLeadingWs = true;
        } else if (prevText) {
          // Drop protection if set previously.
          keepLeadingWs = false;
        }
      } else {
        node = remove(node);
        continue;
      }

      var nextNode = next(prev, node, isPre);
      prev = node;
      node = nextNode;
    }

    if (prevText) {
      prevText.data = prevText.data.replace(/ $/, "");
      if (!prevText.data) {
        remove(prevText);
      }
    }
  }

  /**
   * remove(node) removes the given node from the DOM and returns the
   * next node in the sequence.
   *
   * @param {Node} node
   * @return {Node} node
   */
  function remove(node) {
    var next = node.nextSibling || node.parentNode;

    node.parentNode.removeChild(node);

    return next;
  }

  /**
   * next(prev, current, isPre) returns the next node in the sequence, given the
   * current and previous nodes.
   *
   * @param {Node} prev
   * @param {Node} current
   * @param {Function} isPre
   * @return {Node}
   */
  function next(prev, current, isPre) {
    if ((prev && prev.parentNode === current) || isPre(current)) {
      return current.nextSibling || current.parentNode;
    }

    return current.firstChild || current.nextSibling || current.parentNode;
  }

  /*
   * Set up window for Node.js
   */

  var root = typeof window !== "undefined" ? window : {};

  /*
   * Parsing HTML strings
   */

  function canParseHTMLNatively() {
    var Parser = root.DOMParser;
    var canParse = false;

    // Adapted from https://gist.github.com/1129031
    // Firefox/Opera/IE throw errors on unsupported types
    try {
      // WebKit returns null on unsupported types
      if (new Parser().parseFromString("", "text/html")) {
        canParse = true;
      }
    } catch (e) {}

    return canParse;
  }

  function createHTMLParser() {
    var Parser = function () {};

    {
      if (shouldUseActiveX()) {
        Parser.prototype.parseFromString = function (string) {
          var doc = new window.ActiveXObject("htmlfile");
          doc.designMode = "on"; // disable on-page scripts
          doc.open();
          doc.write(string);
          doc.close();
          return doc;
        };
      } else {
        Parser.prototype.parseFromString = function (string) {
          var doc = document.implementation.createHTMLDocument("");
          doc.open();
          doc.write(string);
          doc.close();
          return doc;
        };
      }
    }
    return Parser;
  }

  function shouldUseActiveX() {
    var useActiveX = false;
    try {
      document.implementation.createHTMLDocument("").open();
    } catch (e) {
      if (root.ActiveXObject) useActiveX = true;
    }
    return useActiveX;
  }

  var HTMLParser = canParseHTMLNatively() ? root.DOMParser : createHTMLParser();

  function RootNode(input, options) {
    var root;
    if (typeof input === "string") {
      var doc = htmlParser().parseFromString(
        // DOM parsers arrange elements in the <head> and <body>.
        // Wrapping in a custom element ensures elements are reliably arranged in
        // a single element.
        '<x-turndown id="turndown-root">' + input + "</x-turndown>",
        "text/html"
      );
      root = doc.getElementById("turndown-root");
    } else {
      root = input.cloneNode(true);
    }
    collapseWhitespace({
      element: root,
      isBlock: isBlock,
      isVoid: isVoid,
      isPre: options.preformattedCode ? isPreOrCode : null,
    });

    return root;
  }

  var _htmlParser;
  function htmlParser() {
    _htmlParser = _htmlParser || new HTMLParser();
    return _htmlParser;
  }

  function isPreOrCode(node) {
    return node.nodeName === "PRE" || node.nodeName === "CODE";
  }

  function Node(node, options) {
    node.isBlock = isBlock(node);
    node.isCode = node.nodeName === "CODE" || node.parentNode.isCode;
    node.isBlank = isBlank(node);
    node.flankingWhitespace = flankingWhitespace(node, options);
    return node;
  }

  function isBlank(node) {
    return (
      !isVoid(node) && !isMeaningfulWhenBlank(node) && /^\s*$/i.test(node.textContent) && !hasVoid(node) && !hasMeaningfulWhenBlank(node)
    );
  }

  function flankingWhitespace(node, options) {
    if (node.isBlock || (options.preformattedCode && node.isCode)) {
      return { leading: "", trailing: "" };
    }

    var edges = edgeWhitespace(node.textContent);

    // abandon leading ASCII WS if left-flanked by ASCII WS
    if (edges.leadingAscii && isFlankedByWhitespace("left", node, options)) {
      edges.leading = edges.leadingNonAscii;
    }

    // abandon trailing ASCII WS if right-flanked by ASCII WS
    if (edges.trailingAscii && isFlankedByWhitespace("right", node, options)) {
      edges.trailing = edges.trailingNonAscii;
    }

    return { leading: edges.leading, trailing: edges.trailing };
  }

  function edgeWhitespace(string) {
    var m = string.match(/^(([ \t\r\n]*)(\s*))(?:(?=\S)[\s\S]*\S)?((\s*?)([ \t\r\n]*))$/);
    return {
      leading: m[1], // whole string for whitespace-only strings
      leadingAscii: m[2],
      leadingNonAscii: m[3],
      trailing: m[4], // empty for whitespace-only strings
      trailingNonAscii: m[5],
      trailingAscii: m[6],
    };
  }

  function isFlankedByWhitespace(side, node, options) {
    var sibling;
    var regExp;
    var isFlanked;

    if (side === "left") {
      sibling = node.previousSibling;
      regExp = / $/;
    } else {
      sibling = node.nextSibling;
      regExp = /^ /;
    }

    if (sibling) {
      if (sibling.nodeType === 3) {
        isFlanked = regExp.test(sibling.nodeValue);
      } else if (options.preformattedCode && sibling.nodeName === "CODE") {
        isFlanked = false;
      } else if (sibling.nodeType === 1 && !isBlock(sibling)) {
        isFlanked = regExp.test(sibling.textContent);
      }
    }
    return isFlanked;
  }

  var reduce = Array.prototype.reduce;
  var escapes = [
    [/\\/g, "\\\\"],
    [/\*/g, "\\*"],
    [/^-/g, "\\-"],
    [/^\+ /g, "\\+ "],
    [/^(=+)/g, "\\$1"],
    [/^(#{1,6}) /g, "\\$1 "],
    [/`/g, "\\`"],
    [/^~~~/g, "\\~~~"],
    [/\[/g, "\\["],
    [/\]/g, "\\]"],
    [/^>/g, "\\>"],
    [/_/g, "\\_"],
    [/^(\d+)\. /g, "$1\\. "],
  ];

  function TurndownService(options) {
    if (!(this instanceof TurndownService)) return new TurndownService(options);

    var defaults = {
      rules: rules,
      headingStyle: "setext",
      hr: "* * *",
      bulletListMarker: "*",
      codeBlockStyle: "indented",
      fence: "```",
      emDelimiter: "_",
      strongDelimiter: "**",
      linkStyle: "inlined",
      linkReferenceStyle: "full",
      br: "  ",
      preformattedCode: false,
      blankReplacement: function (content, node) {
        return node.isBlock ? "\n\n" : "";
      },
      keepReplacement: function (content, node) {
        return node.isBlock ? "\n\n" + node.outerHTML + "\n\n" : node.outerHTML;
      },
      defaultReplacement: function (content, node) {
        return node.isBlock ? "\n\n" + content + "\n\n" : content;
      },
    };
    this.options = extend({}, defaults, options);
    this.rules = new Rules(this.options);
  }

  TurndownService.prototype = {
    /**
     * The entry point for converting a string or DOM node to Markdown
     * @public
     * @param {String|HTMLElement} input The string or DOM node to convert
     * @returns A Markdown representation of the input
     * @type String
     */

    turndown: function (input) {
      if (!canConvert(input)) {
        throw new TypeError(input + " is not a string, or an element/document/fragment node.");
      }

      if (input === "") return "";

      var output = process.call(this, new RootNode(input, this.options));
      return postProcess.call(this, output);
    },

    /**
     * Add one or more plugins
     * @public
     * @param {Function|Array} plugin The plugin or array of plugins to add
     * @returns The Turndown instance for chaining
     * @type Object
     */

    use: function (plugin) {
      if (Array.isArray(plugin)) {
        for (var i = 0; i < plugin.length; i++) this.use(plugin[i]);
      } else if (typeof plugin === "function") {
        plugin(this);
      } else {
        throw new TypeError("plugin must be a Function or an Array of Functions");
      }
      return this;
    },

    /**
     * Adds a rule
     * @public
     * @param {String} key The unique key of the rule
     * @param {Object} rule The rule
     * @returns The Turndown instance for chaining
     * @type Object
     */

    addRule: function (key, rule) {
      this.rules.add(key, rule);
      return this;
    },

    /**
     * Keep a node (as HTML) that matches the filter
     * @public
     * @param {String|Array|Function} filter The unique key of the rule
     * @returns The Turndown instance for chaining
     * @type Object
     */

    keep: function (filter) {
      this.rules.keep(filter);
      return this;
    },

    /**
     * Remove a node that matches the filter
     * @public
     * @param {String|Array|Function} filter The unique key of the rule
     * @returns The Turndown instance for chaining
     * @type Object
     */

    remove: function (filter) {
      this.rules.remove(filter);
      return this;
    },

    /**
     * Escapes Markdown syntax
     * @public
     * @param {String} string The string to escape
     * @returns A string with Markdown syntax escaped
     * @type String
     */

    escape: function (string) {
      return escapes.reduce(function (accumulator, escape) {
        return accumulator.replace(escape[0], escape[1]);
      }, string);
    },
  };

  /**
   * Reduces a DOM node down to its Markdown string equivalent
   * @private
   * @param {HTMLElement} parentNode The node to convert
   * @returns A Markdown representation of the node
   * @type String
   */

  function process(parentNode) {
    var self = this;
    return reduce.call(
      parentNode.childNodes,
      function (output, node) {
        node = new Node(node, self.options);

        var replacement = "";
        if (node.nodeType === 3) {
          replacement = node.isCode ? node.nodeValue : self.escape(node.nodeValue);
        } else if (node.nodeType === 1) {
          replacement = replacementForNode.call(self, node);
        }

        return join(output, replacement);
      },
      ""
    );
  }

  /**
   * Appends strings as each rule requires and trims the output
   * @private
   * @param {String} output The conversion output
   * @returns A trimmed version of the ouput
   * @type String
   */

  function postProcess(output) {
    var self = this;
    this.rules.forEach(function (rule) {
      if (typeof rule.append === "function") {
        output = join(output, rule.append(self.options));
      }
    });

    return output.replace(/^[\t\r\n]+/, "").replace(/[\t\r\n\s]+$/, "");
  }

  /**
   * Converts an element node to its Markdown equivalent
   * @private
   * @param {HTMLElement} node The node to convert
   * @returns A Markdown representation of the node
   * @type String
   */

  function replacementForNode(node) {
    var rule = this.rules.forNode(node);
    var content = process.call(this, node);
    var whitespace = node.flankingWhitespace;
    if (whitespace.leading || whitespace.trailing) content = content.trim();
    return whitespace.leading + rule.replacement(content, node, this.options) + whitespace.trailing;
  }

  /**
   * Joins replacement to the current output with appropriate number of new lines
   * @private
   * @param {String} output The current conversion output
   * @param {String} replacement The string to append to the output
   * @returns Joined output
   * @type String
   */

  function join(output, replacement) {
    var s1 = trimTrailingNewlines(output);
    var s2 = trimLeadingNewlines(replacement);
    var nls = Math.max(output.length - s1.length, replacement.length - s2.length);
    var separator = "\n\n".substring(0, nls);

    return s1 + separator + s2;
  }

  /**
   * Determines whether an input can be converted
   * @private
   * @param {String|HTMLElement} input Describe this parameter
   * @returns Describe what it returns
   * @type String|Object|Array|Boolean|Number
   */

  function canConvert(input) {
    return (
      input != null &&
      (typeof input === "string" || (input.nodeType && (input.nodeType === 1 || input.nodeType === 9 || input.nodeType === 11)))
    );
  }

  return TurndownService;
})();