Infinite Scroll

Load nhentai gallery images vertically with API + fallback extension support, fixed fallback logic

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 or Violentmonkey 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         Infinite Scroll
// @namespace    http://tampermonkey.net/
// @version      1.1
// @description  Load nhentai gallery images vertically with API + fallback extension support, fixed fallback logic
// @author       Duc Anh
// @match        https://nhentai.net/g/*/
// @require      https://code.jquery.com/jquery-3.5.1.min.js
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

    const bigcontainer = $('.thumbs');
    if (!bigcontainer.length) return;

    function getBaseURL() {
        let start = "https://i";
        let maxI = 4;
        let randomI = Math.floor(Math.random() * maxI) + 1;
        let end = ".nhentai.net/galleries/";
        return start + randomI + end;
    }

    let id = location.pathname.split("/")[2];
    fetch("https://nhentai.net/api/gallery/" + id)
        .then(response => {
            if (!response.ok) {
                throw new Error("Could not get page's data!");
            }
            return response.json();
        })
        .then(jsonData => {
            let mediaCode = jsonData.media_id;
            let numPages = jsonData.num_pages;

            let baseUrl = getBaseURL() + mediaCode + "/";

            // Clear old grid
            bigcontainer.empty();
            bigcontainer.css({
                'display': 'flex',
                'flex-direction': 'column',
                'align-items': 'center',
                'gap': '20px',
                'padding': '20px',
                'background': '#111'
            });

            // Insert images one by one
            for (let i = 1; i <= numPages; i++) {
                let img = document.createElement('img');

                let fallbacks = [
                    baseUrl + i + ".webp",
                    baseUrl + i + ".jpg",
                    baseUrl + i + ".png",
                    baseUrl + i + ".gif"
                ];

                let fallbackIndex = 0;

                img.onerror = function() {
                    fallbackIndex++;
                    if (fallbackIndex < fallbacks.length) {
                        this.src = fallbacks[fallbackIndex];
                    }
                };

                // Append BEFORE setting src to ensure it shows even if first fails
                bigcontainer.append(img);

                // Set the initial src AFTER appending and onerror
                img.src = fallbacks[fallbackIndex];

                img.style.maxWidth = '90%';
                img.style.boxShadow = '0 0 10px rgba(0,0,0,0.5)';
                img.loading = 'lazy';
            }
        })
        .catch(error => {
            console.error("nHentai Vertical Scroll: ", error);
        });
})();