基于滚动忽略最后一节的jQuery类更改 [英] jQuery class change based on scroll ignoring last section

问题描述

我正在使用jQuery引导页面滚动并更改导航项的颜色以与您所在的部分相对应.一切正常，但是脚本忽略了页面的最后部分(联系).

I'm using jQuery to guide my pages scrolling and change the color of a nav item to correspond to the section you're in. Everything's working well, but the script is ignoring the last section on the page (Contact).

这很大程度上是基于Stack上的另一个问题，但是我已经修改了代码以适合自己的需求，然后遇到了这个问题.

This is largely based on another question here on Stack, but I've modified the code to fit my needs and then ran into the issue.

测试地点: http://dev4.dhut.ch/

HTML:

<nav>
    <ul>
        <li class="active"><a href="#music" title="Music">MUSIC</a></li>
        <li><a href="#photos" title="Photos">PHOTOS</a></li>
        <li><a href="#lyrics" title="Lyrics">LYRICS</a></li>
        <li><a href="#news" title="News">NEWS</a></li>
        <li><a href="#info" title="Info">INFO</a></li>
        <li><a href='#contact' title="Contact">CONTACT</a></li>
    </ul>
    <span></span>
</nav>

JavaScript:

JavaScript:

var $sections    = $('section'),
    $navs        = $('nav > ul > li'),
    topsArray    = $sections.map(function(){
                       return $(this).position().top - 100;
                   }).get(),
    len          = topsArray.length,
    currentIndex = 0,
    getCurrent   = function(top){
                       for(var i = 0; i < len; i++){
                           if(top > topsArray[i] && topsArray[i+1] && top < topsArray[i+1]){
                               return i;
                           }
                       }
                   };

$(document).scroll(function(e){
    var scrollTop  = $(this).scrollTop(),
        checkIndex = getCurrent( scrollTop );

    if( checkIndex !== currentIndex ){
        currentIndex = checkIndex;
        $navs.eq( currentIndex ).addClass('active').siblings('.active').removeClass('active');
    }
});

推荐答案

我认为问题出在以下几行:

I think the following line is where the problem lies:

if(top > topsArray[i] && topsArray[i+1] && top < topsArray[i+1]){

特别是对于i的最后一次迭代，未定义topsArray[i+1].尝试将包括整个页面高度的另一个值推入topsArray中.

Specifically topsArray[i+1] is undefined for the last iteration of i. Try pushing one more value into topsArray that includes the height of the entire page.

topsArray = $sections.map(function(){
               return $(this).position().top - 100;
            }).get(),
topsArray.push(document.height);

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