Advent of Code Day Navigation Links

This adds forward and backwards links to each day's page.

As of 2025-01-06. See the latest version.

You will need to install an extension such as Tampermonkey, Greasemonkey or Violentmonkey to install this script.

You will need to install an extension such as Tampermonkey to install this script.

You will need to install an extension such as Tampermonkey or Violentmonkey to install this script.

You will need to install an extension such as Tampermonkey or Userscripts to install this script.

You will need to install an extension such as Tampermonkey to install this script.

You will need to install a user script manager extension to install this script.

(I already have a user script manager, let me install it!)

You will need to install an extension such as Stylus to install this style.

You will need to install an extension such as Stylus to install this style.

You will need to install an extension such as Stylus to install this style.

You will need to install a user style manager extension to install this style.

You will need to install a user style manager extension to install this style.

You will need to install a user style manager extension to install this style.

(I already have a user style manager, let me install it!)

// ==UserScript==
// @name        Advent of Code Day Navigation Links
// @namespace   Violentmonkey Scripts
// @match       https://adventofcode.com/*/day/*
// @grant       none
// @version     1.0
// @author      -
// @description This adds forward and backwards links to each day's page.
// ==/UserScript==

/**
 * Return the url of the requested day.
 * If less than 1 or greater than 25 provide a url to the overview page.
 * @param {number} day
 * @returns {string} A url to the requested day
 */
function makeURL(day) {
    if (day < 1 || day > 25) {
        return window.location.href.replace(/\/day\/.*/, '');
    }
    return window.location.href.replace(/(?<=\/day\/).*/, day);
}

/**
 * Create an anchor tag.
 * @param {number} day 
 * @param {string} text 
 * @returns {HTMLAnchorElement}
 */
function makeAnchor(day, text) {
    const anchor = document.createElement('a');
    anchor.href = makeURL(day);
    anchor.textContent = text;
    return anchor
}

/**
 * Find the title, extract the day number, replace the `---` with links.
 */
function addNavigationLinks() {
    const title = document.querySelector('article.day-desc > h2');
    const currentDay = parseInt(title.textContent.match(/(?<=Day )[0-9]+(?=:)/)[0]);
    title.textContent = title.textContent.match(/^--- (.*?) ---$/)[1];
    title.prepend(makeAnchor(currentDay - 1, '<-- '));
    title.append(makeAnchor(currentDay + 1, ' -->'));
}

addNavigationLinks();