Fix input validation and timer handling in alarm clock

Author: khalidbih

Sprint-3/alarmclock/alarmclock.js

@@ -1,11 +1,21 @@
-function setAlarm() {
-  let timer;
+let timer;
 
+function setAlarm() {
   const input = document.getElementById("alarmSet").value;
   let timeLeft = Number(input);
 
   updateDisplay(timeLeft);
 
+  if (input === "" || isNaN(timeLeft)) {
+    return;
+  }
+
+  if (timeLeft < 0) {
+    return;
+  }
+
+  updateDisplay(timeLeft);
+
   clearInterval(timer);
 
   timer = setInterval(() => {
@@ -24,6 +34,10 @@ function setAlarm() {
 function updateDisplay(secondsLeft) {
   const heading = document.getElementById("timeRemaining");
 
+  if (secondsLeft < 0) {
+    secondsLeft = 0;
+  }
+
   const minutes = Math.floor(secondsLeft / 60);
   const seconds = secondsLeft % 60;