javascript - jQuery - 减少滚动边距

Question

我需要减少 .logo-box 的边距和 .frame 的不透明度，直到 .logo-box 的顶部满足.main-nav(两者之间的空间将为 0)，同时用户向下滚动。

相反，页面似乎在变大并变黑，而不是不透明度逐渐降低。

笔:http://codepen.io/abenjamin/pen/LNWwXG

HTML

<header class="page-header">
  <div id="collapse" class="frame">
    <nav class="main-nav container">
      <ul>
        <li><a href="#" class="active">Stuff</a></li>
        <li><a href="#">Explore</a></li>
        <li><a href="#">Activity</a></li>
        <li><a href="#">Messages</a></li>
        <li><a href="#">Help</a></li>
      </ul>
      <div class="user"><span class="name">Aaron Benjamin</span><span class="avatar"></span></div>
    </nav>
    <div class="logo-box container">                            
      <div class="logo">
        <h1>Things!</h1>
        <div class="drop-down">My Stuff</div>
      </div><a href="#" title="New Thing" class="fab">+</a>
    </div>
  </div>
</header>
<div class="utils"></div>

CSS

body {
  font-family: "Open Sans", arial, sans-serif;
  position: relative;
}

.clear {
  clear: both;
}

.container {
  max-width: 960px;
  margin: 0 auto;
}

.sticky {
  position: fixed !important;
  top: 0;
  right: 0;
  left: 0;
}

.page-header {
  background-image: url("https://static.pexels.com/photos/26372/pexels-photo.jpg");
  background-position: bottom center;
  background-size: cover;
  position: fixed;
  top: 0;
  right: 0;
  left: 0;
}
.page-header .frame {
  background: rgba(0, 0, 0, 0.4);
}
.page-header .main-nav {
  padding: 10px 0;
  font-size: 12px;
  color: white;
  line-height: 28px;
  overflow: hidden;
}
.page-header .main-nav ul {
  float: left;
}
.page-header .main-nav ul li {
  display: inline-block;
}
.page-header .main-nav ul li a {
  display: block;
  color: white;
  text-decoration: none;
  opacity: 0.5;
}
.page-header .main-nav ul li a:hover {
  opacity: 1;
}
.page-header .main-nav ul li .active {
  opacity: 1;
}
.page-header .main-nav ul li + li {
  margin-left: 15px;
}
.page-header .main-nav .user {
  float: right;
}
.page-header .main-nav .user span {
  display: block;
  float: left;
}
.page-header .main-nav .user .avatar {
  height: 30px;
  width: 30px;
  background: pink;
  border-radius: 50%;
  margin-left: 10px;
}
.page-header .logo-box {
  margin-top: 300px;
  position: relative;
}
.page-header .logo {
  padding: 20px 0;
  clear: both;
  position: relative;
  overflow: hidden;
}
.page-header .logo h1 {
  float: left;
  background-image: url("/assets/img/studio_logo.png");
  background-size: contain;
  height: 50px;
  width: 209px;
  text-indent: 100%;
  overflow: hidden;
  white-space: nowrap;
}
.page-header .logo .drop-down {
  float: left;
  color: white;
  margin-left: 15px;
  border-left: solid 1px rgba(255, 255, 255, 0.3);
  padding-left: 15px;
  line-height: 50px;
}
.page-header .fab {
  position: absolute;
  bottom: -33px;
  right: 0;
  background: pink;
  border-radius: 50%;
  height: 70px;
  width: 70px;
  clear: both;
  text-align: center;
  line-height: 70px;
  text-decoration: none;
  color: white;
  font-size: 40px;
}

.utils {
  height: 2000px;
}

JS

$(window).scroll(function(){
    var fromTop = $(window).scrollTop(),
        space   = $('.logo-box').offset().top - $('.main-nav').offset().top,
        alpha   = 1;

        if (space > 0) {
            $(".logo-box").css('margin', + (space - 1) + 'px auto 0 auto');
            $(".frame").css('background-color', 'rgba(0,0,0,' + (alpha + 0.1) + ')');
        } 
        console.log(space);
});

Answer 1

使用这段代码似乎可以完成你想要的。

$(window).scroll(function() {
    var requiredOffset = 300;

    // Between 0 and 1 (inclusive)
    var percentage = Math.min(1, $(window).scrollTop() / requiredOffset);

    // Starts at requiredOffset and goes down to 0        
    var marginTop = requiredOffset * (1 - percentage);

    // Opacity of frame
    var alpha = percentage;

    $(".logo-box").css('margin-top', marginTop);
    $(".frame").css('background-color', 'rgba(0,0,0,' + alpha + ')');
});

这是我的 fork 笔:http://codepen.io/dehli/pen/GZmKJO