jQuery Mask Plugin - Issue Report

You don't need to start from scratch..

HTML

<script src="http://igorescobar.github.io/jQuery-Mask-Plugin/js/jquery.mask.min.js"></script>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.1/css/bootstrap.min.css">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.1/css/bootstrap-theme.min.css">
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.1/js/bootstrap.min.js"></script>
<div class="container">
    
    <form role="form">
        
        <div class="form-group">
            <input type="text" id="telefone"/>
        </div>
    
    </form>
</div>

JavaScript

$('#telefone').mask("(00) K0000-0000", {
    placeholder: "(__) 9____-____",
    translation: {
        'K': {
            pattern: /9/,
            fallback: '9'
        }
    }
});