steam cases

// ==UserScript==
// @name         Cases Calc
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  try to take over the world!
// @author       You
// @match        https://steamcommunity.com/*
// @grant        none
// ==/UserScript==

(function () {
    'use strict';

    // Your code here...
    console.log('hello!');

    function write(btn) {
        const priceList = JSON.parse(localStorage.getItem('priceList')) || [];

        let block = document.querySelector('#tabContentsMyMarketHistoryTable');



        if (btn !== 'all') {
            const chkbx = document.querySelectorAll('.chkb_for_add');

            chkbx.forEach(item => {
                if (item.checked == true) {
                    const row = item.parentNode.parentNode;
                    const name = row.querySelector('.market_listing_item_name').innerText;
                    const price = row.querySelector('.market_listing_price').innerText.replace(',', ".").replace('₴', '');

                    const priceItem = {
                        name,
                        count: 1,
                        price
                    };

                    priceList.push(priceItem);

                    item.checked = false;
                }
            })
        } else {
            let items = block.querySelectorAll('.status__');

            items.forEach(item => {

                const row = item.parentNode;

                const name = row.querySelector('.market_listing_item_name').innerText;
                const price = row.querySelector('.market_listing_price').innerText.replace(',', ".").replace('₴', '');

                const priceItem = {
                    name,
                    count: 1,
                    price
                };

                priceList.push(priceItem);
            })
        }


        localStorage.setItem('priceList', JSON.stringify(priceList));

        getReadyArray();
    }


    ///////////////////////////////////////////////////////////

    function getReadyArray() {
        let priceListHistory = '[{"name":"TRIUMPH CRATE","count":1,"price":"1.27"},{"name":"TRIUMPH CRATE","count":1,"price":"1.28"},{"name":"TRIUMPH CRATE","count":1,"price":"1.28"},{"name":"TRIUMPH CRATE","count":1,"price":"1.28"},{"name":"TRIUMPH CRATE","count":1,"price":"1.28"},{"name":"TRIUMPH CRATE","count":1,"price":"1.28"},{"name":"DESPERADO CRATE","count":1,"price":"0.72"},{"name":"EQUINOX CRATE","count":1,"price":"1.87"},{"name":"EQUINOX CRATE","count":1,"price":"1.87"},{"name":"5 EQUINOX CRATE","count":1,"price":"9.45"},{"name":"EQUINOX CRATE","count":1,"price":"1.78"},{"name":"EQUINOX CRATE","count":1,"price":"1.78"},{"name":"EQUINOX CRATE","count":1,"price":"1.78"},{"name":"EQUINOX CRATE","count":1,"price":"1.78"},{"name":"TRIUMPH CRATE","count":1,"price":"2.15"},{"name":"TRIUMPH CRATE","count":1,"price":"2.19"},{"name":"TRIUMPH CRATE","count":1,"price":"2.22"},{"name":"TRIUMPH CRATE","count":1,"price":"2.14"},{"name":"TRIUMPH CRATE","count":1,"price":"2.15"},{"name":"TRIUMPH CRATE","count":1,"price":"2.15"},{"name":"TRIUMPH CRATE","count":1,"price":"2.15"},{"name":"TRIUMPH CRATE","count":1,"price":"2.24"},{"name":"TRIUMPH CRATE","count":1,"price":"2.23"},{"name":"TRIUMPH CRATE","count":1,"price":"2.23"},{"name":"TRIUMPH CRATE","count":1,"price":"2.23"},{"name":"20 TRIUMPH CRATE","count":1,"price":"45.20"},{"name":"TRIUMPH CRATE","count":1,"price":"2.15"},{"name":"TRIUMPH CRATE","count":1,"price":"2.14"},{"name":"TRIUMPH CRATE","count":1,"price":"2.25"},{"name":"TRIUMPH CRATE","count":1,"price":"2.16"},{"name":"TRIUMPH CRATE","count":1,"price":"2.15"},{"name":"TRIUMPH CRATE","count":1,"price":"2.15"},{"name":"TRIUMPH CRATE","count":1,"price":"2.16"},{"name":"TRIUMPH CRATE","count":1,"price":"2.16"},{"name":"TRIUMPH CRATE","count":1,"price":"2.15"},{"name":"DESPERADO CRATE","count":1,"price":"0.71"},{"name":"DESPERADO CRATE","count":1,"price":"0.71"},{"name":"DESPERADO CRATE","count":1,"price":"0.71"},{"name":"DESPERADO CRATE","count":1,"price":"0.71"},{"name":"DESPERADO CRATE","count":1,"price":"0.71"},{"name":"DESPERADO CRATE","count":1,"price":"0.71"},{"name":"DESPERADO CRATE","count":1,"price":"0.71"},{"name":"DESPERADO CRATE","count":1,"price":"0.71"},{"name":"DESPERADO CRATE","count":1,"price":"0.71"},{"name":"40 FEVER CRATE","count":1,"price":"75.20"},{"name":"TRIUMPH CRATE","count":1,"price":"2.80"},{"name":"TRIUMPH CRATE","count":1,"price":"2.80"},{"name":"TRIUMPH CRATE","count":1,"price":"2.80"},{"name":"TRIUMPH CRATE","count":1,"price":"2.77"},{"name":"TRIUMPH CRATE","count":1,"price":"2.80"},{"name":"TRIUMPH CRATE","count":1,"price":"2.80"},{"name":"TRIUMPH CRATE","count":1,"price":"2.80"},{"name":"TRIUMPH CRATE","count":1,"price":"2.80"},{"name":"TRIUMPH CRATE","count":1,"price":"2.80"},{"name":"TRIUMPH CRATE","count":1,"price":"2.80"},{"name":"TRIUMPH CRATE","count":1,"price":"2.80"},{"name":"TRIUMPH CRATE","count":1,"price":"2.80"},{"name":"TRIUMPH CRATE","count":1,"price":"2.80"},{"name":"TRIUMPH CRATE","count":1,"price":"2.80"},{"name":"TRIUMPH CRATE","count":1,"price":"2.80"},{"name":"TRIUMPH CRATE","count":1,"price":"2.80"},{"name":"TRIUMPH CRATE","count":1,"price":"2.50"},{"name":"TRIUMPH CRATE","count":1,"price":"2.80"},{"name":"TRIUMPH CRATE","count":1,"price":"2.80"},{"name":"TRIUMPH CRATE","count":1,"price":"2.50"},{"name":"EQUINOX CRATE","count":1,"price":"1.43"},{"name":"EQUINOX CRATE","count":1,"price":"1.53"},{"name":"EQUINOX CRATE","count":1,"price":"1.43"},{"name":"EQUINOX CRATE","count":1,"price":"1.51"},{"name":"EQUINOX CRATE","count":1,"price":"1.53"},{"name":"EQUINOX CRATE","count":1,"price":"1.51"},{"name":"EQUINOX CRATE","count":1,"price":"1.53"},{"name":"EQUINOX CRATE","count":1,"price":"1.51"},{"name":"EQUINOX CRATE","count":1,"price":"1.43"},{"name":"EQUINOX CRATE","count":1,"price":"1.51"},{"name":"EQUINOX CRATE","count":1,"price":"1.51"},{"name":"EQUINOX CRATE","count":1,"price":"1.43"},{"name":"EQUINOX CRATE","count":1,"price":"1.51"},{"name":"EQUINOX CRATE","count":1,"price":"1.53"},{"name":"EQUINOX CRATE","count":1,"price":"1.43"},{"name":"EQUINOX CRATE","count":1,"price":"1.53"},{"name":"EQUINOX CRATE","count":1,"price":"1.43"},{"name":"EQUINOX CRATE","count":1,"price":"1.53"},{"name":"EQUINOX CRATE","count":1,"price":"1.51"},{"name":"24 EQUINOX CRATE","count":1,"price":"41.76"},{"name":"EQUINOX CRATE","count":1,"price":"1.73"},{"name":"EQUINOX CRATE","count":1,"price":"1.72"},{"name":"EQUINOX CRATE","count":1,"price":"1.72"},{"name":"EQUINOX CRATE","count":1,"price":"1.72"},{"name":"EQUINOX CRATE","count":1,"price":"1.72"},{"name":"EQUINOX CRATE","count":1,"price":"1.72"},{"name":"EQUINOX CRATE","count":1,"price":"1.65"},{"name":"EQUINOX CRATE","count":1,"price":"1.65"},{"name":"10 FEVER CRATE","count":1,"price":"12.90"},{"name":"10 EQUINOX CRATE","count":1,"price":"13"},{"name":"FEVER CRATE","count":1,"price":"1.21"},{"name":"FEVER CRATE","count":1,"price":"1.21"},{"name":"FEVER CRATE","count":1,"price":"1.21"},{"name":"FEVER CRATE","count":1,"price":"1.21"},{"name":"FEVER CRATE","count":1,"price":"1.21"},{"name":"FEVER CRATE","count":1,"price":"1.21"},{"name":"FEVER CRATE","count":1,"price":"1.21"},{"name":"FEVER CRATE","count":1,"price":"1.21"},{"name":"FEVER CRATE","count":1,"price":"1.21"},{"name":"FEVER CRATE","count":1,"price":"1.21"}]'
        let priceListJSON = localStorage.getItem('priceList') || priceListHistory;
        const priceList = JSON.parse(priceListJSON);


        let newList = priceList.map(item => {
            let ifNumber = item.name.split(" ");



            if (!isNaN(+ifNumber[0])) {

                item.count = +ifNumber[0];
                ifNumber.shift();

                item.name = ifNumber.join(" ");
                item.price = item.price / item.count;
            }

            item.price = +item.price;

            return item;
        })

        let lastList = [];

        newList.forEach(item => {
            let obj = lastList.find(obj => obj.name == item.name && obj.price == item.price);

            // console.log(obj);

            if (typeof obj == 'undefined') {
                const toAdd = {};

                toAdd.name = item.name;
                toAdd.count = item.count;
                toAdd.price = item.price;

                lastList.push(toAdd);
            } else {
                obj.count += item.count;
            }
        })

        const finishList = lastList.sort((a, b) => a.count - b.count).reverse();


        localStorage.setItem('priceListFinished', JSON.stringify(finishList));

        console.table(JSON.parse(localStorage.getItem('priceListFinished')));
    }

    function renderHtml() {
        const viewListBtn = document.createElement('a');
        const viewList = document.createElement('div');
        const hiddenBlock = document.createElement('div');
        const body = document.querySelector('body');

        hiddenBlock.style.display = 'none';

        viewListBtn.className = "btn_profile_action btn_medium";
        viewListBtn.innerText = "Чекнуть кейсы";

        viewListBtn.style.position = 'absolute';
        viewListBtn.style.padding = '6px 12px';
        viewListBtn.style.top = '15px';
        viewListBtn.style.right = '15px';
        viewListBtn.style.zIndex = '2';

        viewList.style.position = 'absolute';
        viewList.style.padding = '6px 12px';
        viewList.style.top = '100px';
        viewList.style.right = '10%';
        viewList.style.width = '80vw';
        viewList.style.background = '#3c3c3c';
        viewList.style.display = 'none';
        viewList.style.zIndex = '9999999';

        body.prepend(viewListBtn);
        body.prepend(viewList);


        viewListBtn.addEventListener('click', event => {

            const myItems = JSON.parse(localStorage.getItem('priceListFinished'));

            let response = fetch('https://steamcommunity.com/market/search?appid=578080&q=CRATE');

            response.then(result => {
                return result.text();
            }).then(html => {

                hiddenBlock.innerHTML = html;

                let items = hiddenBlock.querySelectorAll('.market_listing_searchresult');

                const freshPrices = [];

                items.forEach(item => {
                    const name = item.getAttribute('data-hash-name');
                    const price = item.querySelector('.normal_price > .normal_price').getAttribute('data-price') / 100;

                    // console.log(item.querySelector('.normal_price'));

                    freshPrices.push({
                        name,
                        price
                    })
                })

                viewList.innerHTML = `<h1> Лист кейсов </h1>
                                        <table border="1px" style="margin: 20px auto; width: 80%;">
                                            <thead>
                                                <tr>
                                                    <th>Название</th>
                                                    <th>Количество</th>
                                                    <th>Купил</th>
                                                    <th>Сейчас</th>
                                                </tr>
                                            </thead>
                                            <tbody></tbody>
                                            <tfoot></tfoot>
                                        </table>
                                    `;

                const tbody = viewList.querySelector('tbody');
                const tfoot = viewList.querySelector('tfoot');
                let buy = 0,
                    now = 0;

                myItems.forEach(item => {

                    let obj = freshPrices.find(obj => obj.name == item.name);

                    if (typeof obj !== 'undefined') {
                        item.fresh = obj.price;
                    }

                    item.price = Math.round(item.price * 100) / 100;

                    buy += item.price * item.count;
                    now += item.fresh * item.count;


                    tbody.insertAdjacentHTML('beforeEnd', `<tr>
                                    <td>${item.name}</td>
                                    <td>${item.count}</td>
                                    <td>${item.price}</td>
                                    <td>${item.fresh}</td>
                                </tr>`)
                })


                let mathResult = now * 0.87;
                mathResult = Math.round(mathResult * 100) / 100

                tfoot.insertAdjacentHTML('beforeEnd', `<tr>
                <td colspan=2 style="text-align: center;"><strong>Закуплено на </strong> ${buy} грн</td>
                <td colspan=2 style="text-align: center;"><strong>Продашь за </strong> ${mathResult} грн</td>
            </tr>`)

                viewList.style.display = 'block';



            })
        });
    }


    function marketHtml() {
        const tab = document.querySelector("#tabMyMarketHistory");
        let addBtn = document.createElement('a'),
            addAllBtn = document.createElement('a');

        addBtn.classList.add('item_market_action_button', 'item_market_action_button_green', 'item_market_action_button_contents');
        addBtn.innerText = "Добавить в купленные";
        addBtn.style.background = "url('https://steamcommunity-a.akamaihd.net/public/images/economy/btn_green_small.png')"
        addBtn.style.backgroundRepeat = 'repeat-x';
        addBtn.style.backgroundPosition = "left bottom";
        addBtn.style.marginRight = "50px";

        addAllBtn.classList.add('item_market_action_but`ton', 'item_market_action_button_green', 'item_market_action_button_contents');
        addAllBtn.innerText = "Добавить ВСЕ купленные";
        addAllBtn.style.background = "url('https://steamcommunity-a.akamaihd.net/public/images/economy/btn_green_small.png')"
        addAllBtn.style.backgroundRepeat = 'repeat-x';
        addAllBtn.style.backgroundPosition = "left bottom";
        addAllBtn.style.marginRight = "50px";


        tab.addEventListener("click", function () {
            setTimeout(() => {
                let block = document.querySelector('#tabContentsMyMarketHistoryTable'),
                    items = block.querySelectorAll('.market_recent_listing_row'),
                    pagination = document.querySelector("#tabContentsMyMarketHistory_links"),
                    buttonArea = document.querySelector('.pick_and_sell_button');

                items.forEach(item => {

                    const status = item.querySelector('.market_listing_gainorloss').innerText;
                    if (status === "+") {
                        item.querySelector('.market_listing_gainorloss').classList.add("status__");
                        const chkbx = document.createElement('div');
                        chkbx.classList.add('market_listing_left_cell', 'market_listing_gainorloss');

                        chkbx.innerHTML = ' <input type="checkbox" class="chkb_for_add">';

                        item.prepend(chkbx);
                    }
                })

                buttonArea.prepend(addBtn);
                buttonArea.prepend(addAllBtn);

                pagination.addEventListener("click", function () {
                    setTimeout(() => {
                        let block = document.querySelector('#tabContentsMyMarketHistoryTable'),
                            items = block.querySelectorAll('.market_recent_listing_row'),
                            pagination = document.querySelector("#tabContentsMyMarketHistory_links"),
                            buttonArea = document.querySelector('.pick_and_sell_button');

                        items.forEach(item => {

                            const status = item.querySelector('.market_listing_gainorloss').innerText;
                            if (status === "+") {
                                item.querySelector('.market_listing_gainorloss').classList.add("status__");
                                const chkbx = document.createElement('div');
                                chkbx.classList.add('market_listing_left_cell', 'market_listing_gainorloss');

                                chkbx.innerHTML = ' <input type="checkbox" class="chkb_for_add">';

                                item.prepend(chkbx);
                            }
                        })

                        buttonArea.prepend(addBtn);
                        buttonArea.prepend(addAllBtn);

                    }, 2000)
                });
            }, 2000)
        });

        addBtn.addEventListener("click", function () {
            write();
        });

        addAllBtn.addEventListener("click", function () {
            write('all');
        });

    }


    // Запуск функций
    renderHtml();
    marketHtml();
})();

What exactly does this script do?