Bootstrap modal: is not a function

Solution 1:

You have an issue in scripts order. Load them in this order:

<!-- jQuery -->
<script src="//code.jquery.com/jquery-1.11.0.min.js"></script>
<!-- BS JavaScript -->
<script type="text/javascript" src="js/bootstrap.js"></script>
<!-- Have fun using Bootstrap JS -->
<script type="text/javascript">
$(window).load(function() {
    $('#prizePopup').modal('show');
});
</script>

Why this? Because Bootstrap JS depends on jQuery:

Plugin dependencies

Some plugins and CSS components depend on other plugins. If you include plugins individually, make sure to check for these dependencies in the docs. Also note that all plugins depend on jQuery (this means jQuery must be included before the plugin files).

Solution 2:

This warning may also be shown if jQuery is declared more than once in your code. The second jQuery declaration prevents bootstrap.js from working correctly.

<script src="//code.jquery.com/jquery-1.11.0.min.js"></script>
<script type="text/javascript" src="js/bootstrap.js"></script>
...
<script src="//code.jquery.com/jquery-1.11.0.min.js"></script>