diff --git a/.eslintrc.js b/.eslintrc.js
index 9e80f9a..81bee71 100644
--- a/.eslintrc.js
+++ b/.eslintrc.js
@@ -3,7 +3,7 @@ module.exports = {
         "browser": true,
         "es2021": true,
         "mocha": true,
-        "request": true
+        "node": true
     },
     "extends": "eslint:recommended",
     "overrides": [
@@ -13,5 +13,9 @@ module.exports = {
         "sourceType": "module"
     },
     "rules": {
+    },
+    "globals": {
+        "expect": true,
+        "request": true
     }
 }
diff --git a/api/controller.js b/api/controller.js
index 949731c..797d0f7 100644
--- a/api/controller.js
+++ b/api/controller.js
@@ -29,13 +29,13 @@ exports.calculate = function(req, res) {
   }
 
   if (!req.query.operand1 ||
-      !req.query.operand1.match(/^(-)?[0-9\.]+(e(-)?[0-9]+)?$/) ||
+      !req.query.operand1.match(/^(-)?[0-9.]+(e(-)?[0-9]+)?$/) ||
       req.query.operand1.replace(/[-0-9e]/g, '').length > 1) {
     throw new Error("Invalid operand1: " + req.query.operand1);
   }
 
   if (!req.query.operand2 ||
-      !req.query.operand2.match(/^(-)?[0-9\.]+(e(-)?[0-9]+)?$/) ||
+      !req.query.operand2.match(/^(-)?[0-9.]+(e(-)?[0-9]+)?$/) ||
       req.query.operand2.replace(/[-0-9e]/g, '').length > 1) {
     throw new Error("Invalid operand2: " + req.query.operand2);
   }