Revision ae811d92-a6be-4db5-a883-7e43921814b7

I created a program that determines how many years you left before retiring, and in a year when you can retire.
This is my code below:

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

    $(function(){
    	const currentYear = (new Date).getFullYear();
    	var convert = function(a){
    	    return parseInt(a.val());
    	}
    	var result = function(a, b){
    	    $('.currentYear').text(currentYear);
    	    if (b>a){
    		$('.newAge').text(b - a);
    		$('.retireYear').text(currentYear + (b - a));
    		message1.dialog("open");
    		return message1
    	    } else {
    		$('.newAge').text(a - b);
    		$('.retireYear').text(currentYear - (a - b));
    		message2.dialog("open");
    		return message2
    	    }
    	}
    	const message1 = $("#message1").dialog({autoOpen: false});
    	const message2 = $("#message2").dialog({autoOpen: false});
            const form = $("#form").dialog({
                autoOpen: false,
                modal: true,
                buttons:[{
                	text: "Сount",
                	icon: "ui-icon-contact",
                	click: function(){
                	    $( this ).dialog( "close" );
                        var str1 = convert($('#currentAge'));
                        var str2 = convert($('#retireAge'));
                        result(str1, str2);
                	}
                }]
            });
            $("#btn").click(function(){
        	    form.dialog("open");
        	});
    });

<!-- language: lang-html -->

    <link href="https://code.jquery.com/ui/1.12.1/themes/base/jquery-ui.css" rel="stylesheet"/>
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
    <script src="//code.jquery.com/ui/1.12.1/jquery-ui.js"></script>
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/css/bootstrap.min.css" integrity="sha384-rwoIResjU2yc3z8GV/NPeZWAv56rSmLldC3R/AZzGRnGxQQKnKkoFVhFQhNUwEyJ" crossorigin="anonymous">

    <body>
    <div class="container text-center m-5">
    	<button type="button" class="btn btn-primary" id="btn">Retirement Calculator</button>
    </div>

    <form id="form">
        <div class="form-group">
            <label>What is your current age?</label>
            <input type="number" class="form-control" id="currentAge" oninput="validity.valid||(value='');" min="0" style="width: 90px">  
        </div>
        <div class="form-group">
            <label>At what age would you like to retire?</label>
            <input type="number" class="form-control" id="retireAge" oninput="validity.valid||(value='');" min="0" style="width: 90px">  
        </div>
    </form>

    <div id="message1">
    	<p>You have <span class="newAge"></span> years left until you can retire.</p>
    	<p>It's <span class="currentYear"></span>, so you can retire in <span class="retireYear"></span>.</p>
    </div>
    <div id="message2">
    	<p>You could retire <span class="newAge"></span> years ago.</p>
    	<p>It's <span class="currentYear"></span>, so you could retire in <span class="retireYear"></span>.</p>
    </div>
    </body>

<!-- end snippet -->

I will appreciate any advice about code.