mailto in javascript

HTML

<form>
<input id="message" />
</form>
<button>mailto</button>

CSS

body {
    margin: 20px;
}

JavaScript

var body_message = $('#message').value;
var email = '[email protected]';
var subject = 'js email';
$('button').click(function() {

    var mailto_link = 'mailto:[email protected]';


});