使用jQuery更改取决于滚动位置的类 [英] Use jQuery to change a class dependent on scroll position

问题描述

我有一个单页网站，该网站具有固定的浮动导航.我希望能够通过在相关导航中添加一个标记为"on"的类来突出显示用户位于哪个部分.

I have a single page website which has a fixed floating nav. I want to be able to highlight which section the user is on by adding a class of say "on" to the relevant navigation a tag.

当用户不再位于该部分上并且需要在导航栏中反映新的当前部分时，将需要删除此类.

This class will need to be removed when the user is no longer on that section and the new current section then needs to be reflected in the nav.

这不能通过单击功能来完成，因为用户仍然可以只在页面上上下滚动.我知道这个方法是否可以完成，或者因为我的jQuery受限制而从哪里开始.

This can't be done via a click function, as the user could still just scroll up and down the page. I have know idea if this can even be done or where to start as my jQuery is VERY limited.

任何帮助将不胜感激.

这是我当前的网页，没有任何有效的导航突出显示: http ://ec2.dragonstaff.com/www.creativegems.co.uk/

Here is my current webpage, which doesn't have any active nav highlighting: http://ec2.dragonstaff.com/www.creativegems.co.uk/

推荐答案

这似乎与您的网站兼容:

This seems to work with your site:

var $sections = $('section');  // all content sections
var $navs = $('nav > ul > li');  // all nav sections

var topsArray = $sections.map(function() {
    return $(this).position().top - 300;  // make array of the tops of content
}).get();                                 //   sections, with some padding to
                                          //   change the class a little sooner
var len = topsArray.length;  // quantity of total sections
var currentIndex = 0;        // current section selected

var getCurrent = function( top ) {   // take the current top position, and see which
    for( var i = 0; i < len; i++ ) {   // index should be displayed
        if( top > topsArray[i] && topsArray[i+1] && top < topsArray[i+1] ) {
            return i;
        }
    }
};

   // on scroll,  call the getCurrent() function above, and see if we are in the
   //    current displayed section. If not, add the "selected" class to the
   //    current nav, and remove it from the previous "selected" nav
$(document).scroll(function(e) {
    var scrollTop = $(this).scrollTop();
    var checkIndex = getCurrent( scrollTop );
    if( checkIndex !== currentIndex ) {
        currentIndex = checkIndex;
        $navs.eq( currentIndex ).addClass("selected").siblings(".selected").removeClass("selected");
    }
});

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