credit card form

HTML

<input type="text" id="test_form" />

JavaScript

$('#test_form').on('keyup', function(e){
		var val = $(this).val();
    var newval = '';
		val = val.replace(/\s/g, '');
    for(var i=0; i < val.length; i++) {
    	if(i%4 == 0 && i > 0) newval = newval.concat(' ');
      newval = newval.concat(val[i]);
    }
    $(this).val(newval);
	})