variant with preact instead of vanilla js

index.html

@@ -6,11 +6,7 @@
   </head>
   <body>
     <h1>GDG Counter Website</h1>
-    <div class="app">
-      <div id="counter-value">???</div>
-      <button id="btn-decrement">Decrementa</button>  
-      <button id="btn-increment">Incrementa</button>
-    </div>
-    <script type="module" src="/src/main.js"></script>
+    <div id="app"></div>
+    <script type="module" src="/src/main.jsx"></script>
   </body>
 </html>

main.go

@@ -21,6 +21,10 @@ func main() {
 }
 
 func setupRoutes(mux *http.ServeMux) {
+	counter := 0
+
+	// API Routes
+
 	mux.HandleFunc("/api/status", func(w http.ResponseWriter, r *http.Request) {
 		if r.Method != http.MethodGet {
 			http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
@@ -36,6 +40,52 @@ func setupRoutes(mux *http.ServeMux) {
 		}
 	})
 
+	mux.HandleFunc("/api/value", func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodGet {
+			http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
+			return
+		}
+
+		w.Header().Set("Content-Type", "application/json")
+		err := json.NewEncoder(w).Encode(counter)
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+	})
+
+	mux.HandleFunc("/api/increment", func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodPost {
+			http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
+			return
+		}
+
+		counter++
+
+		w.Header().Set("Content-Type", "application/json")
+		err := json.NewEncoder(w).Encode(counter)
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+	})
+
+	mux.HandleFunc("/api/decrement", func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodPost {
+			http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
+			return
+		}
+
+		counter--
+
+		w.Header().Set("Content-Type", "application/json")
+		err := json.NewEncoder(w).Encode(counter)
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+	})
+
 	// Static Files
 	mux.Handle("/", http.FileServer(http.Dir("./dist/")))
 }

package.json

@@ -6,6 +6,10 @@
         "build": "vite build"
     },
     "devDependencies": {
+        "@preact/preset-vite": "^2.5.0",
         "vite": "^3.2.3"
+    },
+    "dependencies": {
+        "preact": "^10.13.0"
     }
 }

src/main.js

@@ -1,27 +0,0 @@
-const counterElement = document.querySelector('#counter-value')
-const incrementButton = document.querySelector('#btn-increment')
-const decrementButton = document.querySelector('#btn-decrement')
-
-function updateCounter(value) {
-    counterElement.textContent = `Counter: ${value}`
-}
-
-incrementButton.addEventListener('click', async () => {
-    const res = await fetch('/api/increment', { method: 'POST' })
-    const data = await res.json()
-    updateCounter(data)
-})
-
-decrementButton.addEventListener('click', async () => {
-    const res = await fetch('/api/decrement', { method: 'POST' })
-    const data = await res.json()
-    updateCounter(data)
-})
-
-async function main() {
-    const res = await fetch('/api/value')
-    const data = await res.json()
-    updateCounter(data)
-}
-
-main()

src/main.jsx

@@ -0,0 +1,38 @@
+import { render } from 'preact'
+import { useState, useEffect } from 'preact/hooks'
+
+const App = ({}) => {
+    const [counter, setCounter] = useState(0)
+
+    useEffect(() => {
+        fetch('/api/value')
+            .then(res => res.json())
+            .then(count => setCounter(count))
+    }, [])
+
+    return (
+        <>
+            <div>{counter}</div>
+            <button
+                onClick={() => {
+                    fetch('/api/decrement', { method: 'POST' })
+                        .then(res => res.json())
+                        .then(count => setCounter(count))
+                }}
+            >
+                Decrementa
+            </button>
+            <button
+                onClick={() => {
+                    fetch('/api/increment', { method: 'POST' })
+                        .then(res => res.json())
+                        .then(count => setCounter(count))
+                }}
+            >
+                Incrementa
+            </button>
+        </>
+    )
+}
+
+render(<App />, document.querySelector('#app'))

vite.config.js

@@ -1,7 +1,12 @@
+import preactPlugin from '@preact/preset-vite'
 import { defineConfig } from 'vite'
 
 export default defineConfig({
     server: {
         port: 3000,
+        proxy: {
+            '/api': 'http://localhost:4000/',
+        },
     },
+    plugins: [preactPlugin()],
 })