如何使固定元素保持相对于当前顶部滚动位置？

Question

原始问题：

我有一个函数，在提示时打开一个覆盖的fixed定位元素，我试图弄清楚如何能够在当前的top位置打开它，而不是每次都跳到页面顶部（top: 0） .no-scroll课程很活跃。

到目前为止，这是我取得的进展：

var o = 0;
$("img.click").click(function() {
  var s = $("html, body");
  o = $(window).scrollTop(), s.css("position", "fixed"), s.css("background-position", "0 -" + o + "px");
  var i = $(this).attr("src");
  s.find("#img-open").attr("src", i), s.addClass("no-scroll"), $("#img-view").addClass("target");
});

而且我还在.no-scroll和html标签上应用了body类：

html {
  height: initial;
}

body {
  height: auto;
}

body.no-scroll,
html.no-scroll {
  overflow: hidden;
  -webkit-overflow-scrolling: touch;
}

更新（Snippet的应用答案+附加说明）：

感谢this answer，我能够调整一些额外的东西：

no-scroll标签上不需要html类。因此，它被删除了。
我将preventDefault()添加到touchmove触摸事件中，这使得body背景内容不会在ios Safari等移动浏览器上滚动（截至2018年）。

$(document).ready(function() {
  $("a.lbimg > img.lb-click").click(function() {
    $("#lb-view").addClass("target");
    var o = document.documentElement.scrollTop || document.body.scrollTop;
    $('body').addClass('no-scroll');
    document.documentElement.scrollTop = document.body.scrollTop = o;
    $('body').bind('touchmove', function(e) {
      e.preventDefault();
    });
  });
  $(".lbimg-wrap, #lb-controls").on("click", function(s) {
    $("#lb-view").removeClass("target");
    $('body').removeClass('no-scroll');
    $('body').unbind('touchmove');
  });
});

body {
  height: auto;
}

body,
html {
  width: 100%;
  background-size: cover;
  background-repeat: no-repeat;
}

body {
  background: #808080;
  margin: 0;
  padding: 0;
  border: 0;
}

body.no-scroll {
  overflow: hidden;
}

p.content {
  color: white;
}

img {
  padding: 5px;
  border: 1px solid;
  box-sizing: border-box;
  z-index: 1;
}

.img-wrap {
  display: block;
}

.img-wrap img {
  line-height: 0;
  display: block;
}

a.lbimg {
  cursor: pointer;
  display: block;
  line-height: 0;
}

a.lbimg img {
  margin: 0 auto;
  padding: 0;
  border: 0;
}

.lb-click {
  width: 25%;
  height: auto;
}

.customlightbox {
  top: 0;
  bottom: 0;
  -webkit-box-sizing: border-box;
  box-sizing: border-box;
  position: fixed;
  left: 0;
  right: 0;
  background: rgba(0, 0, 0, 0.7);
  opacity: 0;
  z-index: -1;
}

.lbimg-wrap {
  width: 100%;
  height: 100%;
  padding: 47px;
  -webkit-box-sizing: border-box;
  box-sizing: border-box;
  position: relative;
  text-align: center;
}

.customlightbox img {
  border-color: white;
  width: auto;
  margin: auto;
  max-width: 100%;
  max-height: 100%;
  opacity: 0;
  position: relative;
  top: 50%;
  -webkit-transform: translateY(-50%);
  -ms-transform: translateY(-50%);
  transform: translateY(-50%);
}

#lb-controls {
  cursor: pointer;
  -webkit-box-sizing: border-box;
  box-sizing: border-box;
  position: fixed;
  height: 50px;
  width: 50px;
  top: -50px;
  right: -3px;
  border-left: 1px solid;
  border-bottom: 1px solid;
  border-color: white;
  z-index: 3;
}

#lb-close {
  display: block;
  position: absolute;
  overflow: hidden;
  height: 30px;
  width: 30px;
  right: 10px;
  top: 10px;
  -webkit-transform: rotate(45deg);
  -ms-transform: rotate(45deg);
  transform: rotate(45deg);
}

#lb-close:before,
#lb-close:after {
  content: '';
  display: block;
  position: absolute;
  background: white;
  -webkit-border-radius: 2px;
  -moz-border-radius: 2px;
  border-radius: 2px;
}

#lb-close:before {
  width: 2px;
  height: 0;
  top: 0;
  left: 14px;
}

#lb-close:after {
  width: 0;
  height: 2px;
  top: 14px;
  left: 0;
}

.customlightbox.target {
  display: inline-block;
  z-index: 2;
}

.customlightbox.target,
.customlightbox.target img {
  opacity: 1;
}

.customlightbox.target~#lb-controls {
  top: -3px;
}

.customlightbox.target~#lb-controls #lb-close:after {
  width: 30px;
}

.customlightbox.target~#lb-controls #lb-close:before {
  height: 30px;
}

.lb-animate {
  -webkit-transition: 0.5s ease-in-out;
  -o-transition: 0.5s ease-in-out;
  transition: 0.5s ease-in-out;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<body>

  <p class="content">
    Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content
    to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content
    to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content
    to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content
    to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content
    to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll.
  </p>

  <div class="img-wrap">
    <a class="lbimg">
      <img class="lb-click" src="https://78.media.tumblr.com/8b1b8cbb2b963ab64eb2341f608638bf/tumblr_p4wbo7ZLJS1qccr26o1_1280.jpg">
    </a>
    <div class="customlightbox lb-animate" id="lb-view">
      <div class="lbimg-wrap">
        <img class="lb-animate" id="lbimg-open" src="https://78.media.tumblr.com/8b1b8cbb2b963ab64eb2341f608638bf/tumblr_p4wbo7ZLJS1qccr26o1_1280.jpg">
      </div>
    </div>
    <div id="lb-controls" class="lb-animate">
      <a id="lb-close" class="lb-animate"></a>
    </div>
  </div>

  <p class="content">
    Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content
    to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content
    to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content
    to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content
    to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content
    to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll. Content to scroll.
  </p>

</body>