Question

当您从页面顶部向下滚动时，我试图让导航栏消失，但只要用户向上滚动就会出现。现在，当您到达页面顶部时，代码段会在导航栏中淡出，但我希望它在用户向上滚动时淡入淡出。 JSFiddle

(function ($) {
  $(document).ready(function(){
	$(function () {
		$(window).scroll(function () {
			if ($(this).scrollTop() > 100) {
				$('.navbar').fadeOut();
			} else {
				$('.navbar').fadeIn();
			}
		});
	});
});
  }(jQuery))

body {
    /* for demo purpose only */
    height:2000px;
    padding-top:100px;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"></script>
<nav class="navbar navbar-default navbar-fixed-top " role="navigation">
    <div class="container-fluid">
        <!-- Brand and toggle get grouped for better mobile display -->
        <div class="navbar-header">
            <button type="button" class="navbar-toggle" data-toggle="collapse" data-target="#bs-example-navbar-collapse-1"> <span class="sr-only">Toggle navigation</span>
 <span class="icon-bar"></span>
 <span class="icon-bar"></span>
 <span class="icon-bar"></span>

            </button> <a class="navbar-brand" href="#">Brand</a>

        </div>
        <!-- Collect the nav links, forms, and other content for toggling -->
        <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
            <ul class="nav navbar-nav">
                <li class="active"><a href="#">Link</a>
                </li>
                <li><a href="#">Link</a>
                </li>
                <li class="dropdown"> <a href="#" class="dropdown-toggle" data-toggle="dropdown">Dropdown <b class="caret"></b></a>

                    <ul class="dropdown-menu">
                        <li><a href="#">Action</a>
                        </li>
                        <li><a href="#">Another action</a>
                        </li>
                        <li><a href="#">Something else here</a>
                        </li>
                        <li class="divider"></li>
                        <li><a href="#">Separated link</a>
                        </li>
                        <li class="divider"></li>
                        <li><a href="#">One more separated link</a>
                        </li>
                    </ul>
                </li>
            </ul>
            <form class="navbar-form navbar-left" role="search">
                <div class="form-group">
                    <input type="text" class="form-control" placeholder="Search">
                </div>
                <button type="submit" class="btn btn-default">Submit</button>
            </form>
            <ul class="nav navbar-nav navbar-right">
                <li><a href="#">Link</a>
                </li>
                <li class="dropdown"> <a href="#" class="dropdown-toggle" data-toggle="dropdown">Dropdown <b class="caret"></b></a>

                    <ul class="dropdown-menu">
                        <li><a href="#">Action</a>
                        </li>
                        <li><a href="#">Another action</a>
                        </li>
                        <li><a href="#">Something else here</a>
                        </li>
                        <li class="divider"></li>
                        <li><a href="#">Separated link</a>
                        </li>
                    </ul>
                </li>
            </ul>
        </div>
        <!-- /.navbar-collapse -->
    </div>
    <!-- /.container-fluid -->
</nav>Scroll down to activate menu bar

Answer 1

您必须跟踪上一个滚动位置，然后确定滚动是向上还是向下。

这样的事情应该有效

jQuery(function ($) {
    var t = 0;

    $(window).scroll(function () {
        if ($(this).scrollTop() > 100 && t < $(this).scrollTop() ) {
            $('.navbar').fadeOut();
        } else {
            $('.navbar').fadeIn();
        }

        t = $(this).scrollTop();
    });
});

请注意，您只需要一个DOM就绪函数，而不是三个，在这种情况下，您根本不需要任何函数，因为窗口始终可用。

FIDDLE

ScrollUp上的FadeIn元素

1 个答案: