show errors in demo

Signed-off-by: hrj <harshad.rj@gmail.com>

src/main/resources/index.html

@@ -8,15 +8,24 @@
   </style>
 
 <script>
+  function showError(errMessage) {
+    const resultDiv = document.getElementById("result")
+    const result = `
+      <p>Error: ${errMessage}</p>
+    `
+    resultDiv.innerHTML = result;
+  }
+
   async function loadCaptcha() {
     const levelInput = document.getElementById("levelInput").value
     const mediaInput = document.getElementById("mediaInput").value
     const typeInput = document.getElementById("typeInput").value
-    const resp = await fetch("/v1/captcha", {
+    fetch("/v1/captcha", {
        method: 'POST',
        body: JSON.stringify({level: levelInput, media: mediaInput, "input_type" : typeInput})
-    })
+    }).then(async function(resp) {
       const respJson = await resp.json()
+      if (resp.ok) {
         const id = respJson.id
         const resultDiv = document.getElementById("result")
         const result = `
@@ -27,6 +36,10 @@
           <div id="answerResult" />
         `
         resultDiv.innerHTML = result;
+      } else {
+        showError("Failed with response code: " + resp.status + " response: " + JSON.stringify(respJson))
+      }
+    }).catch(showError)
   }
   async function submitAnswer(id) {
     const ans = document.getElementById("answerInput").value;