fix: prevent variable being declared globally

Fixes #238

js/predictions.js

@@ -882,8 +882,8 @@ class Predictor {
     });
 
     let global_min_max = [];
-    for (var day = 0; day < 14; day++) {
+    for (let day = 0; day < 14; day++) {
-      prices = {
+      const prices = {
         min: 999,
         max: 0,
       }

js/scripts.js

@@ -208,9 +208,8 @@ const getPricesFromQuery = function (param) {
 };
 
 const getPreviousFromQuery = function () {
-
   /* Check if valid prices are entered. Exit immediately if not. */
-  prices = getPricesFromQuery("prices");
+  const prices = getPricesFromQuery("prices");
   if (prices == null) {
     return null;
   }