Try Catch Program
<!DOCTYPE html>
<html>
<head>
<script>
var txt = "";
function message() {
try {
alertMe("Welcome guest!");
} catch (err) {
txt = "There was an error on this page.\n\n";
txt += "Error description: " + err.message + "\n\n";
txt += "Click OK to continue.\n\n";
alert(txt);
}
}
</script>
</head>
<body>
<input type="button" value="View message" onclick="message()" />
</body>
</html>