scrollTop position incorrect when scrolling back to top of window

I am using scrollTop to get the current scroll position of an inner scroll div .content-inner. From here, I am then adding a translate3d to change the position of another div .header-top to give it an animation effect.

The issue I have is after scroll back up on .content-inner the .header-top position is a bit glitchy and not how it originally positioned.

Depending on the speed I scroll back up too will determine how far the position changes. I suspect it's to do with the double negative values outputting on translate3d if you check the console.

See: https://jsfiddle.net/ez379rax/5/

Solution

Yes you are correct, the problem was a negative value in the calculation once you have reached the top.

I have made some changes to the code, remove unnecessary overflows, and capture the window scroll event. Also made the header fits nicely inside the container.

var pos = 0;
var $ = jQuery;

 $(window).on("scroll", function() {

  var st = $(this).scrollTop();
  pos = (1.6 * (-st) - 20);
	
  if(st === 0)
  {
  	pos = 0;
  }

  var up = 'translateY(' + pos + 'px )';

  $(".header").css({
    "transform": up
  });

});

.header{
	  color: #333;
    height: 150px;
    padding: 25px;
    width:100%;
    position: fixed;
		background:cornflowerblue;
    margin:5px;
}

.content-wrap{
	height:100%
}

.content-inner{
		padding-top: 100px;
    height: 100%;
    padding-left: 25px;
    padding-right: 25px;
    -ms-scroll-chaining: none;
    overscroll-behavior: contain;
    -webkit-overflow-scrolling: touch;
    overscroll-behavior: contain;
    -ms-scroll-chaining: none;
    display: block;
		background:#fff
}

.scroll-inner{
	  min-height: calc(100% + 36px);
}

.card{
	margin-bottom:1.5rem;
  width:100%;
	p{
		margin-bottom:0
	}
}

<link href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.2.1/css/bootstrap.css" rel="stylesheet"/>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<body>
  <div class="content-wrap">
    <div class="header">
      <h4>
        Widget Header
      </h4>
    </div>

    <div class="content-inner">
      <div class="scroll-inner">
        <div class="card">
          <div class="card-body">
            <h2>
              Filler Card
            </h2>
            <p>
              Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
            </p>
          </div>
        </div>
        <!-- end of card -->
        <div class="card">
          <div class="card-body">
            <h2>
              Filler Card
            </h2>
            <p>
              Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
            </p>
          </div>
        </div>
        <!-- end of card -->
        <div class="card">
          <div class="card-body">
            <h2>
              Filler Card
            </h2>
            <p>
              Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
            </p>
          </div>
        </div>
        <!-- end of card -->
        <div class="card">
          <div class="card-body">
            <h2>
              Filler Card
            </h2>
            <p>
              Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
            </p>
          </div>
        </div>
        <!-- end of card -->
        <div class="card">
          <div class="card-body">
            <h2>
              Filler Card
            </h2>
            <p>
              Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
            </p>
          </div>
        </div>
        <!-- end of card -->
        <div class="card">
          <div class="card-body">
            <h2>
              Filler Card
            </h2>
            <p>
              Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
            </p>
          </div>
        </div>
        <!-- end of card -->
      </div>
    </div>
  </div>
</body>