Checking for existing accounts when registering

Packed up js into a file

public/auth.html

@@ -25,14 +25,6 @@
   </form>
 
   <script src="https://www.google.com/recaptcha/api.js?render=6LcTXIsaAAAAAGWE4913KuaqU1tTT9uyqmvPADcn"></script>
-  <script>
-    grecaptcha.ready(function () {
-      grecaptcha.execute('6LcTXIsaAAAAAGWE4913KuaqU1tTT9uyqmvPADcn', { action: 'demo' })
-        .then(function (token) {
-          document.getElementsByClassName('g-recaptcha-response')[0].value = token;
-          document.getElementsByClassName('g-recaptcha-response')[1].value = token;
-        });
-    });
-  </script>
+  <script src="index.js"></script>
 </body>
 </html>

public/index.js

@@ -0,0 +1,7 @@
+grecaptcha.ready(function () {
+  grecaptcha.execute('6LcTXIsaAAAAAGWE4913KuaqU1tTT9uyqmvPADcn', { action: 'demo' })
+    .then(function (token) {
+      document.getElementsByClassName('g-recaptcha-response')[0].value = token;
+      document.getElementsByClassName('g-recaptcha-response')[1].value = token;
+    });
+});

server.js

@@ -49,12 +49,19 @@ app.post('/register', async (req, res) => {
   verifyCaptcha(req, res, async () => {
     const hashedPass = await bcrypt.hash(req.body.pass, 10)
     try {
+      const user = await client.db('reg_example').collection('users').findOne({
+        login: req.body.login
+      })
+      if (user) {
+        res.send('A user with this username already exists.')
+      } else {
         await client.db('reg_example').collection('users').insertOne({
           login: req.body.login,
           pass: hashedPass
         })
         req.session.loggedIn = true
         res.status(201).redirect('/')
+      }
     } catch (e) {
       console.log("Error: " + e)
       res.status(500).send()