mdtocs/umd/mdtocs.js

Markdown table of contents generator.

(function (global, factory) {
    typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports) :
    typeof define === 'function' && define.amd ? define(['exports'], factory) :
    (global = typeof globalThis !== 'undefined' ? globalThis : global || self, factory(global.mdtocs = {}));
})(this, (function (exports) { 'use strict';

    const CODE_BLOCK_REGEX = /^```.*\n[\s\S]*?```$/gm;
    const HEADINGS_REGEX = /^(#{1,6}[ \t].+)$|^(.+[\r\n][=-]{3,})$/gm;
    const HEADING_REGEX = /^(#+)[ \t](.+)$|^(.+)[\r\n]([=-])/;
    const INVALID_FRAGMENT_REGEX = /[^a-zA-Z0-9_-]/g;
    const WHITESPACE_REGEX = /\s/;
    const BLANK = '';
    const HYPHEN = '-';
    const NEWLINE = '\n';
    const SPACE = ' ';
    const INDENT = SPACE.repeat(2);
    const BULLET = HYPHEN + SPACE;

    function clean(markdown) {
        return markdown.replace(CODE_BLOCK_REGEX, BLANK).trim();
    }

    function parse(markdown) {
        const headings = markdown.match(HEADINGS_REGEX);
        if (headings === null) {
            return [];
        }
        const fragments = {};
        const initialValue = [];
        return headings.reduce((accumulator, heading) => {
            const [level, text] = getHeadingLevelAndText(heading);
            if (level && text) {
                accumulator.push({
                    level,
                    text,
                    fragment: createFragment(text, fragments),
                });
            }
            return accumulator;
        }, initialValue);
    }
    function getHeadingLevelAndText(heading) {
        const headingMatch = heading.match(HEADING_REGEX);
        if (headingMatch === null) {
            return [];
        }
        const [, headingLevel, headingText, headingTextAlternate, headingLevelAlternate,] = headingMatch;
        let text;
        let level;
        if (headingLevelAlternate) {
            level = headingLevelAlternate === HYPHEN ? 2 : 1;
            text = headingTextAlternate.trim();
        }
        else {
            level = headingLevel.length;
            text = headingText.trim();
        }
        if (!text) {
            return [];
        }
        return [level, text];
    }
    function createFragment(text, fragments) {
        const fragment = text
            .toLowerCase()
            .split(WHITESPACE_REGEX)
            .join('-')
            .replace(INVALID_FRAGMENT_REGEX, '');
        const count = fragments[fragment];
        if (count) {
            fragments[fragment]++;
            return fragment + HYPHEN + count;
        }
        fragments[fragment] = 1;
        return fragment;
    }

    function transform(headings) {
        return headings.reduce((accumulator, heading) => {
            const { level, text, fragment } = heading;
            return (accumulator +
                INDENT.repeat(level - 1) +
                BULLET +
                createLink(text, fragment) +
                NEWLINE);
        }, '');
    }
    function createLink(text, fragment) {
        return '[' + text + '](#' + fragment + ')';
    }

    function validate(markdown) {
        if (typeof markdown !== 'string') {
            throw new TypeError('First argument must be a string');
        }
        return markdown;
    }

    function mdtocs(markdown) {
        return transform(parse(clean(validate(markdown))));
    }

    exports.mdtocs = mdtocs;

}));
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