Legimi.pl - Snippet for adding book to shelf from main catalogue

Legimi.addToShelf.js

// This snippet adds 'Add to Shelf' button while viewing legimi.pl catalogue
// How to add and run snippet:
// https://developers.google.com/web/tools/chrome-devtools/javascript/snippets#runcommandmenu
let books = document.querySelectorAll('.book-box');
books.forEach(book => {
    let link = book.querySelector("a.book-title");
    let url = link.href;
    let bookId = url.slice(url.indexOf(',') + 2, url.lastIndexOf('.'));
    let btn = document.createElement('button');
    btn.setAttribute("onclick", "addToShelf(this)");
    let cssText = "background-color:#4e9af1;display:inline-block;padding:0.3em 1.2em;margin:0 0.1em 0.1em 0;border:0.16em solid rgba(255,255,255,0);border-radius:2em;box-sizing: border-box;text-decoration:none;font-family:'Roboto',sans-serif;font-weight:300;color:#FFFFFF;text-shadow: 0 0.04em 0.04em rgba(0,0,0,0.35);text-align:center;transition: all 0.2s;"
    btn.style.cssText = cssText;
    btn.setAttribute('data-book-id', bookId);
    let bookPanel = book.querySelector('.panel');
    btn.innerText = "Add To Shelf";
    bookPanel.appendChild(btn);
});

function addToShelf(btn) {
    fetch("https://www.legimi.pl/api/shopping/shelf/addbook", {
        method: "POST",
        body: JSON.stringify({
            bookId: Number(btn.dataset.bookId)
        }),
        headers: {
            "Content-Type": "application/json",
            "X-XSRF-Token": window.userInfoAsync.xsrf,
            "authorization": "Basic " + window.logger.apiService.apiKey
        },
        credentials: "same-origin"
    }).then(function(response) {
        if (response.status == 401) {
            buttons = document.querySelectorAll('button[data-book-id]');
            buttons.forEach(button => {
                button.innerText = "Please log in!";
            })
        }

        if (response.ok) {
            return response.json()
        }
    }).then(data => {
            if (data.success == true) {
                btn.innerText = "Added";
                btn.animate([{
                    opacity: 1
                }, {
                    opacity: 0
                }], {
                    duration: 1100,
                    iterations: 1
                }).onfinish = () => btn.remove();
            } else
            {
                btn.innerText = "You already added that book!";
                btn.animate([{
                    opacity: 1
                }, {
                    opacity: 0
                }], {
                    duration: 1100,
                    iterations: 1
                }).onfinish = () => btn.remove();
            }
    }).catch((error) => {})
}
document.styleSheets[document.styleSheets.length - 1].insertRule('button:hover{border-color:rgba(255,255,255,1)!important}')

@globus1987 not exactly. But I did some reverse engineering here and there and have quite a good knowledge of schema