speed up loading

lib/usePrices.js

@@ -13,12 +13,21 @@ export const usePrices = () => {
   const [prices, setPrices] = useState(COUNTRIES);
   useEffect(() => {
     const fetchAll = async () => {
-      for (const [index, country] of COUNTRIES.entries()) {
+      for (let index = 0; index < prices.length; index += 2) {
         // intentionally blocking execution
         // to resolve sequentially.
         // It should prevent DOS and triggering captcha
-        const found = await bookPriceFor(country);
+        if (index + 1 < prices.length) {
-        prices[index] = found;
+          const [first, second] = await Promise.all([
+            bookPriceFor(prices[index]),
+            bookPriceFor(prices[index + 1]),
+          ]);
+          prices[index] = first;
+          prices[index + 1] = second;
+        } else {
+          prices[index] = await bookPriceFor(prices[index]);
+        }
+
         sortPrices(prices);
         setPrices([...prices]);
       }

manifest.json

@@ -1,7 +1,7 @@
 {
   "name": "Kobo Price",
   "description": "Find lowest book price on kobo.com",
-  "version": "1.2.1",
+  "version": "1.2.3",
   "manifest_version": 3,
   "content_scripts": [
     {