...

.env

@@ -0,0 +1 @@
+PORT=4000

eslint.config.mjs

@@ -2,17 +2,17 @@ import globals from "globals";
 import pluginJs from "@eslint/js";
 
 export default [
-  { files: ["**/*.js"], languageOptions: { sourceType: "commonjs" } },
-  { languageOptions: { globals: globals.browser } },
-  pluginJs.configs.recommended,
-  {
-    rules: {
-      "prefer-const": "off",
-      "quotes": ["warn", "double", { "allowTemplateLiterals": true }],
-      "no-unused-vars": "warn",
-      "no-multi-spaces": "warn",
-      "no-multiple-empty-lines": ["warn", { "max": 1 }],
-      "no-case-declarations": "off"
-    }
-  }
+    { files: ["**/*.js"], languageOptions: { sourceType: "commonjs" } },
+    { languageOptions: { globals: { ...globals.browser, ...globals.node } } },
+    pluginJs.configs.recommended,
+    {
+        rules: {
+            "prefer-const": "off",
+            "no-unused-vars": "warn",
+            "no-multi-spaces": "warn",
+            "no-case-declarations": "off",
+            "no-multiple-empty-lines": ["warn", { max: 1 }],
+            quotes: ["warn", "double", { allowTemplateLiterals: true }],
+        },
+    },
 ];

package-lock.json

@@ -9,6 +9,7 @@
       "version": "1.0.0",
       "license": "ISC",
       "dependencies": {
+        "dotenv": "^16.4.5",
         "express": "^4.19.2"
       },
       "devDependencies": {
@@ -601,6 +602,17 @@
         "npm": "1.2.8000 || >= 1.4.16"
       }
     },
+    "node_modules/dotenv": {
+      "version": "16.4.5",
+      "resolved": "https://registry.npmjs.org/dotenv/-/dotenv-16.4.5.tgz",
+      "integrity": "sha512-ZmdL2rui+eB2YwhsWzjInR8LldtZHGDoQ1ugH85ppHKwpUHL7j7rN0Ti9NCnGiQbhaZ11FpR+7ao1dNsmduNUg==",
+      "engines": {
+        "node": ">=12"
+      },
+      "funding": {
+        "url": "https://dotenvx.com"
+      }
+    },
     "node_modules/ee-first": {
       "version": "1.1.1",
       "resolved": "https://registry.npmjs.org/ee-first/-/ee-first-1.1.1.tgz",

package.json

@@ -10,6 +10,7 @@
   "author": "",
   "license": "ISC",
   "dependencies": {
+    "dotenv": "^16.4.5",
     "express": "^4.19.2"
   },
   "devDependencies": {

src/app.js

@@ -1,9 +1,11 @@
+require("dotenv").config();
 const express = require("express");
 
 const app = express();
+const PORT = process.env.PORT
 
 app.use((req, res, next) => {
     res.send("Hello");
 });
 
-app.listen(3000);
+app.listen(PORT);