parse.js

function pageFunction(context) {
  var $ = context.jQuery; // get query context
  var priceElem = $(".shopee-product-info__header__real-price"); // main selector what we are waiting for, mounting

  function delay(selector, callback, count) { // delay function
    if (selector.length && count !== 0) { // if selector is on page and count isnt zero move to get data callback
      return callback(); // get data callback
    } else if (count === 0) {  // if count zero, we are already wait 20*6000 ms do context.skipOutput();
      context.skipOutput(); // i dont know what is that
    } else { // if not previous action then wait 6s and try agin until count === 0 (20 times)
      setTimeout(function () { delay(selector, callback, count - 1); }, 6000);
    }
  }

  function getData() { // this func get text data from fields and return it;
    var regPriceField = $(".shopee-product-info__header__price-before-discount__number"),
      priceField = $(".shopee-product-info__header__real-price"),
      sockField = $(".shopee-product-info-body__order-quantity__stock-count"),
      regPrice, price, stock;
      
    if (regPriceField && regPriceField.length > 0) {
      regPrice = regPriceField.text();
    } else {
      regPrice = 'no data';
    }
    if (priceField && priceField.length > 0) {
      price = priceField.text();
    } else {
      price = 'no data';
    }
    if (sockField && sockField.length > 0) {
      stock = sockField.text().trim();
    } else {
      stock = 'no data';
    }
    return {
      regPrice,
      price,
      stock
    }
  }
  var result = delay(priceElem, getData, 20); // start to cicle func
  return result; // return result from "pageFunction" do with it all waht you want
}