Как повесить события кнопок, чтобы при нажатии они имитровали e.keyCode цифр и клавише bakspace?

$(function() { 
 
  $('input[name="mobile"]').inputmask("+7(999) 999-99-99"); 
 
  $('.numeric-input').keyboard({ 
    layout: 'custom', 
    autoAccept: 'true', 
    customLayout: { 
      'default': [ 
        '7 8 9', 
        '4 5 6', 
        '1 2 3', 
        '0 {bksp}', 
        'accept' 
      ] 
    }, 
    usePreview: false, 
    position: { of: null, // null (attach to input/textarea) or a jQuery object (attach elsewhere) 
      my: 'left top', // keyboard itself 
      at: 'left top', // input or textarea that the keyboard is attached to 
      at2: 'left bottom' // used when "usePreview" is false (centers the keyboard at the bottom of the input/textarea) 
    } 
  }) 
 
 
 
});

<link href="https://cdnjs.cloudflare.com/ajax/libs/virtual-keyboard/1.27.3/css/keyboard.min.css" rel="stylesheet" /> 
 
 
 
 
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> 
<script src="https://cdnjs.cloudflare.com/ajax/libs/jqueryui/1.12.1/jquery-ui.min.js"></script> 
<script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.7/js/bootstrap.min.js"></script> 
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery.inputmask/3.3.4/jquery.inputmask.bundle.min.js"></script> 
<script src="https://cdnjs.cloudflare.com/ajax/libs/virtual-keyboard/1.27.3/js/jquery.keyboard.min.js"></script> 
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery-mousewheel/3.1.13/jquery.mousewheel.min.js"></script> 
<script src="https://cdnjs.cloudflare.com/ajax/libs/virtual-keyboard/1.27.3/js/jquery.keyboard.extension-caret.min.js"></script> 
<script src="https://cdnjs.cloudflare.com/ajax/libs/virtual-keyboard/1.27.3/js/jquery.keyboard.extension-typing.min.js"></script> 
<script src="https://cdnjs.cloudflare.com/ajax/libs/virtual-keyboard/1.27.3/js/jquery.keyboard.extension-previewkeyset.min.js"></script> 
 
 
<input name="mobile" type="text" placeholder="+7(___)___-__-__" class="inptext phone_activation numeric-input" value="+7">