Neopets Create Trade Helper

neopets-create-trade-helper.user.js

// ==UserScript==
// @name         Neopets Create Trade Helper
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  try to take over the world!
// @author       Juvian
// @match        ://www.neopets.com/island/tradingpost*
// @grant        none
// ==/UserScript==

let f = document.querySelector('form[action="/island/process_tradingpost.phtml"]');
let wishlist = document.querySelector('textarea[name="wishlist"]');
let tpPrices;

for (let checkbox of f.querySelectorAll('input[type="checkbox"]')) {
	checkbox.addEventListener('change', (e) => {
		let checked = f.querySelectorAll('input[type="checkbox"]:checked');
		if (checked.length > 10) {
			Array.from(checked).slice(10).forEach(c => c.checked = false);
		}
		if (f && wishlist) updateWishlist();
	})
}

if (f && wishlist) {
	tpPrices = JSON.parse(localStorage.tpPrices || "{}");
	let table = f.closest("table").parentNode.closest("table");
	table.setAttribute('width', 'auto');
	table.style.textAlign ='center';
	let div = table.parentNode;
	div.style.marginLeft = 'auto';
	div.style.marginRight = 'auto';

	f.addEventListener('submit', savePrices);

	for (let row of f.querySelectorAll('tbody tr')) {
	    let input = document.createElement('input');
		let td = document.createElement('td');
		td.setAttribute('bgcolor', '#ffffff');
		input.value = getPrice(getId(row));
		td.appendChild(input);
		input.addEventListener('blur', updateWishlist);
		row.prepend(td);
	}
}

function getId(row) {
	let img = row.querySelector('img');
	let name = img.nextSibling.nodeValue;
	let url = img.getAttribute('src').split('/').pop();
	return name + '-' + url;
}

function setPrice(id, price) {
    tpPrices[id] = price;
}

function savePrices() {
	localStorage.tpPrices = JSON.stringify(tpPrices);
}

function getPrice(id) {
    return tpPrices[id] || '';
}

function updateWishlist() {
	let prices = [];
	let checked = f.querySelectorAll('input[type="checkbox"]:checked');
	let hasInfo = false;
	for (let check of checked) {
		let row = check.closest('tr');
		let input = row.querySelector('input');
		prices.push(input.value || (checked.length == 1 ? '' : "offer"));
		setPrice(getId(row), input.value);
		hasInfo = hasInfo || input.value;
	}

	if(hasInfo) wishlist.value = prices.join(' | ');
}