Steam Mass Sell

// ==UserScript==
// @name         Steam Mass Sell
// @namespace    https://gist.github.com/jaks97/68ed8ede8d493f369918c0956bbdb5ab
// @version      0.1
// @description  Mass sell items on Steam using its own endpoint.
// @require      https://code.jquery.com/jquery-3.3.1.min.js
// @require      https://code.jquery.com/ui/1.12.1/jquery-ui.min.js
// @author       jaks
// @match        *://steamcommunity.com/*/inventory*
// @grant        none
// ==/UserScript=={

this.$ = this.jQuery = jQuery.noConflict(true);

(function () {
    console.log($("#inventory_logos"));
	$("#inventory_logos").append(`<a class="btn_green_white_innerfade btn_medium_wide" id="sell"><span>Pick items to sell</span></a>`);
	$("#sell").click(selectItems);
	$("head").append(`<style>.ui-selected{outline: 2px solid #00adee;}
               .ui-selected .item{ background: #4e4e4e;}
    </style>`);
})();

var selectedItems = [];

function selectItems() {
	$('#inventories').selectable({
		filter: ".itemHolder",
		selected: function (e, ui) {
			if (selectedItems.indexOf(ui.selected) === -1) // We ensure that items do not get duplicated
				selectedItems.push(ui.selected);
			$("#sell").html(`<span>Sell ${selectedItems.length} items</span>`);
		},
		unselected: function (e, ui) {
			selectedItems.splice(selectedItems.indexOf(ui.unselected), 1);
			$("#sell").html(`<span>Sell ${selectedItems.length} items</span>`);
		}
	});
	$("#sell").html(`<span>Sell</span>`).click(sell);
}

function sell() {
    if(selectedItems.length === 0)
        return;

	let items = [];
	for (let i = 0; i < selectedItems.length; i++) {
		if (items.some(item => item.market_hash_name == selectedItems[i].rgItem.description.market_hash_name)) { // We ensure that items do not get duplicated
			items.filter(item => item.market_hash_name == selectedItems[i].rgItem.description.market_hash_name)[0].qty++;
		} else {
			items.push({
				market_hash_name: selectedItems[i].rgItem.description.market_hash_name,
				qty: 1
			});
		}
	}
	let uri = "https://steamcommunity.com/market/multisell?appid=753&contextid=6";
	for (let i = 0; i < items.length; i++) {
		uri += `&items[]=${encodeURIComponent(items[i].market_hash_name)}&qty[]=${items[i].qty}`;
	}
	console.log(items);
	selectedItems = [];
	window.open(uri, '_blank');
}