Display an alert message with jQuery when no option is selected from a dynamically generated drop-down list

Issue

I want to display an alert message when no option is selected from a dropdown list that is generated from PHP.

I have a script that displays an alert message when the text box is left blank as it was static and easy to do although i am having trouble doing the same with the drop down list, basically the dropdown list is a selection of cars that the seller can offer to an interested buyer and changes dynamically.

Any Help would be much appreciated

HTML/PHP

<form method="POST" id="carForm" action="<?= $this->url(array('cid' => $this->cid), 'approach-to-car') ?>">
<?= CSRF::tokenField() ?>
<div class="row-fluid">
    <div class="span2">
        Job:
    </div>
    <div class="span10">
        <select name="car" class="input-block-level">
            <?php foreach ($this->cars as $car): ?>
                <?php $car = Car::getOne($car['id']); ?>
                <?/*@var $car Car */?>
                <option value="<?= $car->id ?>"><?= $car->get_title() ?></option>
            <?php endforeach; ?>
        </select>
    </div>
</div>
<div class="row-fluid">
    <div class="span2">
        Message:
    </div>
    <div class="span10">
        <textarea name="message" rows="5" id="messageInput" class="input-block-level"></textarea>
    </div>
</div>
<div class="row-fluid">
    <div class="offset2">
        <input type="submit" class="btn btn-primary" id="submitButton" value="Approach" />
    </div>
</div>

jQuery

<script type="text/javascript">
$("#carForm").bind('submit', function(e) {
    var messageValue = $("#messageInput").val();
    if (messageValue === "") {
        $("#alertBox").html("Include a message with your offer");
        $("#alertBox").removeClass('hide');
        e.preventDefault();
        return false;
    }
    return true;

});

This is the jQuery script that currently isn't working for me

<script type="text/javascript">
$("#carForm").bind('submit', function(e) {
    var carValue = $("#input-block-level").val();
    if (carValue === "") {
        $("#alertBox").html("Please add your car before offering buyers");
        $("#alertBox").removeClass('hide');
        e.preventDefault();
        return false;
    }
    return true;

});

Solution

Check this: http://jsfiddle.net/5ywey/

var carValue = $(".input-block-level").val();

you try to select by id instead of class.

Answered By - mrcrgl