mindoc/static/turndown/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 <[email protected]>
     *
     * 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;

}());