Common Mistakes, Debugging, and Error Handling - Beginning JavaScript - page 559

</td>
<td>
<a id="usernameAvailability" href="#">Check Availability</a>
</td>
</tr>
<tr>
<td class="fieldname">
Email:
</td>
<td>
<input type="text" id="email" />
</td>
<td>
<a id="emailAvailability" href="#">Check Availability</a>
</td>
</tr>
<tr>
<td class="fieldname">
Password:
</td>
<td>
<input type="text" id="password" />
</td>
<td />
</tr>
<tr>
<td class="fieldname">
Verify Password:
</td>
<td>
<input type="text" id="password2" />
</td>
<td />
</tr>
<tr>
<td colspan="2" class="submit">
<input type="submit" value="Submit" />
</td>
<td />
</tr>
</table>
</form>
<script src="jquery-2.1.1.min.js"></script>
<script>
function checkUsername(e) {
e.preventDefault();
var userValue = $("#username").val();
try {
if (!userValue) {
throw {
message: "Please enter a user name to check!"
};