maskedinput Uncaught TypeError: $(...).mask is not a function

Change this line from

$(document).ready(function(){ 

to

$(document).ready(function($){

I got this same error too, but in my case I forgot to import maskedinput.min.js

<script src="/js/jquery.maskedinput.min.js" type="text/javascript"></script>

And I was searching Google for a solution haha.