Question

如何在滚动jquery期间找到屏幕上的元素。

目前，我正在使用带滚动条的导航栏。当我们自动向下或向上滚动时，应启用导航栏中的链接。

我尝试http://codetheory.in/change-active-state-links-sticky-navigation-scroll/并且能够成功。

一个问题是当链接到达屏幕顶部时启用链接。但是当元素到达屏幕中心时，我需要启用链接。

提前致谢。

Answer 1

只需将窗口高度的一半添加到当前位置：

var cur_pos = $(this).scrollTop() + $(window).height() / 2;

点击链接时减去它：

$('html, body').animate({
    scrollTop: $(id).offset().top - nav_height - $(window).height() / 2
}, 500);

试试这个片段（最好全屏打开）：

var sections = $('section')
  , nav = $('nav')
  , nav_height = nav.outerHeight();

$(window).on('scroll', function () {
  var cur_pos = $(this).scrollTop() + $(window).height() / 2;
  
  sections.each(function() {
    var top = $(this).offset().top - nav_height,
        bottom = top + $(this).outerHeight();
    
    if (cur_pos >= top && cur_pos <= bottom) {
      nav.find('a').removeClass('active');
      sections.removeClass('active');
      
      $(this).addClass('active');
      nav.find('a[href="#'+$(this).attr('id')+'"]').addClass('active');
    }
  });
});

nav.find('a').on('click', function () {
  var $el = $(this)
    , id = $el.attr('href');
  
  $('html, body').animate({
    scrollTop: $(id).offset().top - nav_height - $(window).height() / 2
  }, 500);
  
  return false;
});

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: 'Open Sans', sans-serif;
}

/* Navigation */

nav {
  width: 100%;
  height: 60px; 
  position: fixed; 
  top: 0;
  background: #1ABC9C;
}

nav ul {
  padding: 20px;
  margin: 0 auto;
  list-style: none;
  text-align: center;
}
nav ul li {
  display: inline-block;
  margin: 0 10px;
}
nav ul li a {
  padding: 10px 0;
  color: #fff;
  font-size: 1rem;
  text-decoration: none;
  font-weight: bold;
  transition: all 0.2s ease;
}
nav ul li a:hover {
  color: #34495E;
}
a.active {
  border-bottom: 2px solid #ecf0f1;
}

/* Headings */

h1 {
  font-size: 5rem;
  color: #34495E;
}

/* Sections */

section {
  width: 100%;
  padding: 50px;
  background: #fff;
  border-bottom: 1px solid #ccc;
  height: 500px;
  text-align: center;
}
section:nth-child(even) {
  background: #ecf0f1;
}
section:nth-child(odd) {
  background: #bdc3c7;
}
.sections section:first-child {
  margin-top: 60px;
}
section.active {}

footer {
  height: 500px;
  background: #34495e;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<nav>
  <ul>
    <li><a href="#1" class="active">First</a></li>
    <li><a href="#2">Second</a></li>
    <li><a href="#3">Third</a></li>
    <li><a href="#4">Fourth</a></li>
    <li><a href="#5">Fifth</a></li>
  </ul>
</nav>

<div class="sections">
  <section id="1"><h1>First</h1></section>
  <section id="2"><h1>Second</h1></section>
  <section id="3"><h1>Third</h1></section>
  <section id="4"><h1>Fourth</h1></section>
  <section id="5"><h1>Fifth</h1></section>
</div>

<footer></footer>

Answer 2

您可以尝试以下代码：

var sections = $('section')
  , nav = $('nav')
  , nav_height = nav.outerHeight()
  , win_height = $(window).height();
$(window).on('scroll', function () {
  var cur_pos = $(this).scrollTop();
  sections.each(function() {
    
    var top = $(this).offset().top - nav_height,
        bottom = top + $(this).outerHeight();
 
    if (bottom >= (win_height / 2 + cur_pos) ) {
      nav.find('a').removeClass('active');
      sections.removeClass('active');
      
      $(this).addClass('active');
      nav.find('a[href="#'+$(this).attr('id')+'"]').addClass('active');
      return false;
    }
  });
});

nav.find('a').on('click', function () {
  var $el = $(this)
    , id = $el.attr('href');
  
  $('html, body').animate({
    scrollTop: $(id).offset().top - nav_height
  }, 500);
  
  return false;
});

@import url(https://fonts.googleapis.com/css?family=Open+Sans);

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: 'Open Sans', sans-serif;
}

/* Navigation */

nav {
  width: 100%;
  height: 60px; 
  position: fixed; 
  top: 0;
  background: #1ABC9C;
}

nav ul {
  padding: 20px;
  margin: 0 auto;
  list-style: none;
  text-align: center;
}
nav ul li {
  display: inline-block;
  margin: 0 10px;
}
nav ul li a {
  padding: 10px 0;
  color: #fff;
  font-size: 1rem;
  text-decoration: none;
  font-weight: bold;
  transition: all 0.2s ease;
}
nav ul li a:hover {
  color: #34495E;
}
a.active {
  border-bottom: 2px solid #ecf0f1;
}

/* Headings */

h1 {
  font-size: 5rem;
  color: #34495E;
}

/* Sections */

section {
  width: 100%;
  padding: 50px;
  background: #fff;
  border-bottom: 1px solid #ccc;
  height: 500px;
  text-align: center;
}
section:nth-child(even) {
  background: #ecf0f1;
}
section:nth-child(odd) {
  background: #bdc3c7;
}
.sections section:first-child {
  margin-top: 60px;
}
section.active {}

footer {
  height: 500px;
  background: #34495e;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<nav>
  <ul>
    <li><a href="#1">First</a></li>
    <li><a href="#2">Second</a></li>
    <li><a href="#3">Third</a></li>
    <li><a href="#4">Fourth</a></li>
    <li><a href="#5">Fifth</a></li>
  </ul>
</nav>

<div class="sections">
  <section id="1"><h1>First</h1></section>
  <section id="2"><h1>Second</h1></section>
  <section id="3"><h1>Third</h1></section>
  <section id="4"><h1>Fourth</h1></section>
  <section id="5"><h1>Fifth</h1></section>
</div>

<footer></footer>

<script class="cssdeck" src="//cdnjs.cloudflare.com/ajax/libs/jquery/1.8.0/jquery.min.js"></script>

希望，这有助于：）

如何在滚动jquery期间找到屏幕上的元素

2 个答案: