adding dotenv and envalid to manage environment variable properly

.gitignore

@@ -88,4 +88,4 @@
 /BackEnd/configs/OS.js
 /BackEnd/src/configs/OS.ts
 /BackEnd/dist
-
+/BackEnd/.env*

BackEnd/package.json

@@ -20,7 +20,9 @@
     "body-parser": "^1.19.0",
     "child_process": "^1.0.2",
     "cors": "2.8.5",
+    "dotenv": "^10.0.0",
     "ejs": "3.1.5",
+    "envalid": "^7.1.1",
     "errorhandler": "1.5.1",
     "express": "^4.17.1",
     "express-generator": "^4.16.1",

BackEnd/src/env/db.ts

@@ -0,0 +1,2 @@
+export default {
+}

BackEnd/src/env/index.ts

@@ -0,0 +1,15 @@
+import { cleanEnv, str } from 'envalid';
+
+import serverEnv from './server';
+import dbEnv from './db';
+
+const env = cleanEnv(process.env, {
+  NODE_ENV: str({
+    choices: ["development", "test", "production"],
+  }),
+
+  ...serverEnv,
+  ...dbEnv,
+})
+
+export default env;

BackEnd/src/env/server.ts

@@ -0,0 +1,2 @@
+export default {
+}

BackEnd/src/env/utils.ts

@@ -0,0 +1,11 @@
+export function ownDefault<T>({ dev, test, all } :
+                              {dev : T, test : T, all : T}) {
+  switch(process.env.NODE_ENV) {
+  case "test":
+    return test;
+  case "development":
+    return dev;
+  default:
+    return all;
+  }
+}