handle error when pressing letter key on time fields

src/HMSInput.js

@@ -43,9 +43,14 @@ class HMSInput extends Component {
   someChange(ev) {
     const { onChange } = this.props;
     const { state } = this;
+    if(Number(isNaN(ev.target.value))){
+      return;
+    }else{
+      console.log(Number(ev.target.value));
       state[ev.target.name] = Number(ev.target.value);
       onChange(state.hours * 3600 + state.minutes * 60 + state.seconds);
     }
+  }
 
   /** Add one second by simulating an input change */
   addOneSec() {