how to get the class name dynamically using jquery

JavaScript
<input id="btn" class="wpsc-buy-now-button wpsc-buy-now-button-64" type="image"
    name="submit" border="0" src="https://www.paypal.com/en_US/i/btn/btn_buynow_LG.gif"
    alt="PayPal - The safer, easier way to pay online" />
 $('.setvalue').on('click', function() {
       var id = $(this).data("id");
       var inp =  $('#applicantstatus_' + id).val();var className = $('#id').attr('class');
var $classOfBtn = 'wpsc-buy-now-button-64';
$(document).ready(function () {
    var $classOfBtn = $('#btn').attr('class').split(' ')[0] + '-64';
    alert($classOfBtn );
});
var id = $(this).attr("id")$('.'+$classOfBtn)
var $classOfBtn = wpsc-buy-now-button-64;
$('.' + $classOfBtn) //note the dot
$(document).ready(function () {
    var $allClasses = $("[name='submit']").attr('class').split(' ');
    for(var i=0; i < $allClasses.length; i++)
    {
        // Check $allClasses[i] here.
    }
});

Source

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