Because you are binding it multiple times. Click event inside a click event means every time you click, a new click event is being bound on top of the previously bound events. Do not bind click events inside of click events unless the click event creates the element. There’s also no need to re-initialize the modal over and over.
$(document).ready(function ($) {
$('#confirmCreateModal').modal({show: false});
$('#confirmCreateYes').click(function () {
$('#confirmCreateModal').modal('hide');
var test = "123";
alert(test);
console.log(test);
});
$('.creategene').click(function () {
$('#confirmCreateModal').modal('show');
});
});