Bootstrap 3 modal vertical position center

Question

This is a two part question:

1. How can you position the modal vertically in the center when you don\'t know the exact height of the modal?

2. Is

Answer 1

i have downloaded bootstrap3-dialog from bellow link and modified the open function in bootstrap-dialog.js

https://github.com/nakupanda/bootstrap3-dialog

Code

open: function () {
            !this.isRealized() && this.realize();
            this.updateClosable();
            //Custom To Vertically centering Bootstrap 
            var $mymodal = this.getModal();
            $mymodal = $mymodal.append('');
            $mymodal = $mymodal.find(".modal-dialog").appendTo($mymodal.find(".centerModal"));
            //END
            this.getModal().modal('show');
            return this;
        }

Css

.centerModal .modal-header{
    text-align:left;
}
.centerModal .modal-body{
    text-align:left;
}