Smooth scroll header with fixed position

Question

How to create smooth scroll when I change the position to fixed. I try to add the animation but it does not work. Better use jquery animation();

Answer 1

EDITED based on comment.

If you change position to fixed while scrolling, it will generate undesired jump behavior.

Your best bet would be to prevent positioning while scrolling, setting fixed after 40px or from the start is pretty much the same, so I'd suggest you remove this part on your jQuery, and make your header fixed from the start:

//if (scroll >= 40) sticky.addClass('fixed');
//else sticky.removeClass('fixed');

Snippet below:

$(window).scroll(function() {
  var sticky = $('.mobile-menu'),
    scroll = $(window).scrollTop();
});

body {
  position: relative;
}
header {
  padding: 20px 40px;
  background: gray;
  width: 100%;
  -webkit-transition: position 10s;
  -moz-transition: position 10s;
  -ms-transition: position 10s;
  -o-transition: position 10s;
  transition: position 10s;
}
section {
  height: 150vh;
  position: relative;
  top: 60px;
}
.fixed {
  position: fixed;
  z-index: 1;
  top: 0;
  left: 0;
  right: 0;
  width: 100%;
}

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