Convert environment variable generation script from bash to nodejs

Dockerfile

@@ -2,9 +2,6 @@
 # This image is around 50 megabytes
 FROM node:18-alpine3.18 AS builder
 
-# Environment variable generation script needs bash
-RUN apk add --no-cache bash
-
 # Create app directory
 WORKDIR /app
 
@@ -18,7 +15,7 @@ RUN npm ci --verbose
 RUN npm run build
 
 # Create environment variable js file
-RUN chmod +x env.sh && ./env.sh
+RUN node generate-env-browser.js
 
 ### STAGE 2: Run ###
 # This image is around 5 megabytes

generate-env-browser.js

@@ -0,0 +1,43 @@
+import fs from "node:fs";
+import process from "node:process";
+
+const JS_FILE = "env-config.js";
+const ENV_FILE = ".env";
+
+// Remove existing config file
+if (fs.existsSync(JS_FILE)) {
+  fs.unlinkSync(JS_FILE);
+}
+// Create new file
+fs.writeFileSync(JS_FILE, "", "utf-8");
+
+// Add assignment
+fs.appendFileSync(JS_FILE, "window._env_ = {\n");
+
+// Read each line in .env file
+// Each line represents key=value pairs
+const envFile = fs.readFileSync(ENV_FILE, "utf-8");
+const lines = envFile.split("\n");
+
+lines.forEach((line) => {
+  // Ignore comments, lines starting with hash
+  if (line.startsWith("#")) {
+    return;
+  }
+  // Split env variables by character `=`
+  if (line.includes("=")) {
+    const [varname, varvalue] = line.split("=");
+
+    // Read value of current variable if exists as Environment variable
+    let value = process.env[varname] || varvalue;
+    // Otherwise use value from .env file
+    if (typeof value === "undefined") {
+      value = varvalue;
+    }
+
+    // Append configuration property to JS file
+    fs.appendFileSync(JS_FILE, `  ${varname}: "${value}",\n`);
+  }
+});
+
+fs.appendFileSync(JS_FILE, "};");

package.json

@@ -39,7 +39,7 @@
         "use-image": "^1.1.1"
     },
     "scripts": {
-        "start": "chmod +x ./env.sh && sh ./env.sh && cp env-config.js ./public/ && vite",
+        "start": "node generate-env-browser.js && cp env-config.js ./public/ && vite",
         "test": "jest",
         "build": "vite build",
         "lint": "eslint --ignore-path .gitignore . --ext .ts,.tsx,.jsx,.js",