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Here you can Sed posuere consectetur est at lobortis. Donec ullamcorper nulla non metus auctor fringilla. Maecenas sed diam eget risus varius blandit sit amet non magna. Donec id elit non mi porta gravida at eget metus. Praesent commodo cursus magna, vel scelerisque nisl consectetur et.

    Demo for this article:

<nav class="table-of-contents">

<h1>The Chicago Manual of Style</h1>

<article class="article">
    <p>The Chicago Manual of Style is a style guide…</p>
    <h2>Availability and usage</h2>
    <p>The Chicago Manual of Style is published in hardcover and online…</p>
    <h2>Citation Styles</h2>
    <p>Two types of citation styles are provided…</p>
    <h3>Author-date style</h3>
    <p>Using author-date style…</p>
    <h3>Notes and bibliography style</h3>
    <p>Using notes and bibliography style…</p>
    <p>What now is known as The Chicago Manual of Style…</p>
    <h3>History of editions</h3>
        <li>First Edition, 1906</li>
    <h2>Recent printed editions</h2>
        <li>University of Chicago (2003)</li>
    <h2>See also</h2>
        <li>Linguistic prescription</li>

    Demo for this article:

body {
    font-family: "Arial", sans-serif;

.table-of-contents {
    display: inline-block;
    padding: 0 1em;
    background: #f2f2f2;
    border: 1px solid #ddd;
    font-size: .8em;

/* https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Lists_and_Counters/Using_CSS_counters#Nesting_counters */
.table-of-contents ol {
    list-style: none;
    padding: 0;
    counter-reset: counter-table-of-contents;

.table-of-contents ol ol {
    padding-left: 2em;

.table-of-contents ol li {
    margin: .5em 0;

.table-of-contents ol li::before {
    counter-increment: counter-table-of-contents;
    content: counters(counter-table-of-contents, ".") " ";
    opacity: .7;

    Demo for this article:

class TableOfContents {
        The parameters from and to must be Element objects in the DOM.
    constructor({ from, to }) {
        this.fromElement = from;
        this.toElement = to;
        // Get all the ordered headings.
        this.headingElements = this.fromElement.querySelectorAll("h1, h2, h3, h4, h5, h6");
        this.tocElement = document.createElement("div");

        Get the most important heading level.
        For example if the article has only <h2>, <h3> and <h4> tags
        this method will return 2.
    getMostImportantHeadingLevel() {
        let mostImportantHeadingLevel = 6; // <h6> heading level
        for (let i = 0; i < this.headingElements.length; i++) {
            let headingLevel = TableOfContents.getHeadingLevel(this.headingElements[i]);
            mostImportantHeadingLevel = (headingLevel < mostImportantHeadingLevel) ?
                headingLevel : mostImportantHeadingLevel;
        return mostImportantHeadingLevel;

        Generate a unique id string for the heading from its text content.
    static generateId(headingElement) {
        return headingElement.textContent.replace(/\s+/g, "_");

        Convert <h1> to 1 … <h6> to 6.
    static getHeadingLevel(headingElement) {
        switch (headingElement.tagName.toLowerCase()) {
            case "h1": return 1;
            case "h2": return 2;
            case "h3": return 3;
            case "h4": return 4;
            case "h5": return 5;
            case "h6": return 6;
            default: return 1;

    generateToc() {
        let currentLevel = this.getMostImportantHeadingLevel() - 1,
            currentElement = this.tocElement;

        for (let i = 0; i < this.headingElements.length; i++) {
            let headingElement = this.headingElements[i],
                headingLevel = TableOfContents.getHeadingLevel(headingElement),
                headingLevelDifference = headingLevel - currentLevel,
                linkElement = document.createElement("a");

            if (!headingElement.id) {
                headingElement.id = TableOfContents.generateId(headingElement);
            linkElement.href = `#${headingElement.id}`;
            linkElement.textContent = headingElement.textContent;

            if (headingLevelDifference > 0) {
                // Go down the DOM by adding list elements.
                for (let j = 0; j < headingLevelDifference; j++) {
                    let listElement = document.createElement("ol"),
                        listItemElement = document.createElement("li");
                    currentElement = listItemElement;
            } else {
                // Go up the DOM.
                for (let j = 0; j < -headingLevelDifference; j++) {
                    currentElement = currentElement.parentNode.parentNode;
                let listItemElement = document.createElement("li");
                currentElement = listItemElement;

            currentLevel = headingLevel;


document.addEventListener("DOMContentLoaded", () =>
    new TableOfContents({
        from: document.querySelector(".article"),
        to: document.querySelector(".table-of-contents")

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