changing div height on scroll

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What I want is a div at the top (header) that will be at maximum height (50px) when you first load the page, and when you\'re scrolling down the page I want the height to sm

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被撕碎了的回忆

2021-01-13 13:35

I've added to #body_parent height to see the scroll, you can delete that row with height after you create the site.

Here is jsfiddle

$(window).on('scroll', function () {
    var scrollTop = $(window).scrollTop();
    if (scrollTop > 50) {
        $('#header_parent').stop().animate({height: "30px"},200);
    }
    else {
         $('#header_parent').stop().animate({height: "50px"},200);   
    }
});

* {
    margin:0 auto;
    padding:0;
}

#header_parent {
    max-width:1250px;
    min-width:750px;
    height:50px;
    background:#000;
    position:fixed;
}

#body_parent {
     height:1200px;   
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js"></script>
<body>
    <!-- Header -->
    <div id="header_parent">
        
    </div>
    
    <!-- Body (homepage) -->
    <div id="body_parent">
        
    </div>
    
    <!-- Footer -->
    <div id="footer_parent">
        
    </div>
    
</body>

Or HTML

<html>
    <head>
        <link rel="stylesheet" type="text/css" href="css/main.css">
    </head>

    <body>
        <!-- Header -->
        <div id="header_parent">

        </div>

        <!-- Body (homepage) -->
        <div id="body_parent">

        </div>

        <!-- Footer -->
        <div id="footer_parent">

        </div>

     <!-- jQuery library -->
     <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.2/jquery.min.js"></script>
     <!-- Your jQuery/Javascript code -->
     <script  type="text/javascript">
     $(window).on('scroll', function () {
        var scrollTop = $(window).scrollTop();
        if (scrollTop > 50) {
            $('#header_parent').stop().animate({height: "30px"},200);
        }
        else {
             $('#header_parent').stop().animate({height: "50px"},200);   
        }
     });
     </script>
    </body>
</html>

And if you want to set smoothness replace 200 with your number, 200 mean duration in miliseconds.

$('#header_parent').stop().animate({height: "50px"},200);

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盖世英雄少女心

2021-01-13 13:35

You can do this without jQuery.

var header = document.getElementById("header_parent");

window.onscroll = function(e) {
    if(window.scrollY) {
        if(window.pageYOffset > 50) {
            header.style.height = 30;
        } else {
            header.style.height = 50;
        }
    }
}

You could also toggle class names inside the if block instead of setting the height explicitly.

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