How to make popup disappear smoothly?

Question

css

Good day
https://codepen.io/anon/pen/yKaYVp
There is such an attempt to make the window fade smoothly, but for some reason it does not work, what am I doing wrong?

Answer 1

jquery-3.2.1.min.js

$(document).ready(function(){
  $('.jsdonate').click(function() {
    $('.popup').fadeIn();
  })
  $('.closepop').click(function() {
    $('.popup').fadeOut();
  })
});