allegro-price-per-item.js

// ==UserScript==
// @name         Allegro - cena za sztukę
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  try to take over the world!
// @author       You
// @match        https://allegro.pl/listing*
// @match        https://allegro.pl/oferta*
// @grant        none
// @updateURL    https://gist.githubusercontent.com/M1nified/c5880ed65568d255f5e49745b910aba4/raw/allegro-price-per-item.js
// ==/UserScript==


(function() {
    'use strict';
    const PRICE_BOX_SELECTOR = '._1svub._lf05o',
          TITLE_BOX_SELECTOR = 'h2',
          PRICE_SIBLING_SELECTOR = '._9c44d_1xKGX',
          COUNT_REGEX = /\d+\s*[sS][zZ][tT]/,
          MULTIPLY_REGEX = /\d\s*x\s*\d+\s*[sS][zZ][tT]/;

    const articles = document.querySelectorAll('article');
    articles.forEach(article => {
        try{
            const priceBox = article.querySelector(PRICE_BOX_SELECTOR);
            const titleBox = article.querySelector(TITLE_BOX_SELECTOR);
            if(!priceBox || !titleBox) return;
            const titleText = titleBox.textContent;
            const countTextMatches = titleText.match(COUNT_REGEX);
            if(!countTextMatches) return;
            const [countTextMatch] = countTextMatches;
            const multiplyTextMatches = titleText.match(MULTIPLY_REGEX);
            const multiplyCount = multiplyTextMatches ? Number.parseFloat(multiplyTextMatches[0]) : 1;
            const count = Number.parseInt(countTextMatch) * multiplyCount;
            const priceText = priceBox.textContent.replace(',','.');
            const price = Number.parseFloat(priceText);
            const priceWithShippingBox = article.querySelector(PRICE_SIBLING_SELECTOR);
            const pricePerItemBox = document.createElement('div');
            priceWithShippingBox.after(pricePerItemBox);
            const pricePerItem = Math.round((price/count) * 1000) / 1000;
            pricePerItemBox.innerHTML = `${pricePerItem} zł za sztukę (${count} sztuk)`;
        }catch(e){
            console.error(e);
        }
    });

})();