JQuery $ is not a function

When adding JQuery script in WordPress, the error occurred as $ is not a function.

Fix

Add a function wrapping the $ function as below.

<script type="text/javascript">
    (function($) {
        // You pass-in jQuery and then alias it with the $-sign
        // So your internal code doesn't change
    }) (jQuery);
</script>

References

jquery - is not a function error