javascript - 检测故意的顶部和底部额外滚动

Question

我正在尝试使用 javascript 检测有意的额外顶部/底部滚动。 $(window).scrollTop() 和 window.pageYOffset 没有用，因为它们停在 Top 0 我想达到类似顶部-X。对于底部，假设我的文档的高度为 500，底部将类似于 bottom 5XX。

编辑:示例代码可以是:

$(window).scroll(function(){

  if(intentionalScrollTop){
    // Do something
  }else if(intentionalScrollDown){
    // Do something
  }

});

动图示例:

Answer 1

我从你的问题中了解到的不仅仅是“检测过度滚动”......
但也可以使用它来创建动画，就像您在问题中展示的那样。

正如我 2 天前评论的那样，我使用包装器 div 制作了一个解决方案。

你可以在CodePen中看到它或下面的代码片段。

$(document).ready(function(){
	    
    var at_Top=true;
    var at_Bottom=false;
	var previous_scrolled;
	var triggerTime=0;
    var scroll_dir=false;   // false=>Down true=>up
	var scrolled_bottom = $("body").height() - $(window).height();
	var animationDelay = 300;
	var animationTimeout = 350;		//Max delay between 2 triggers is 1 sec.
									//So keep this value under 400ms
									//Because one complete animation is 300ms+350ms+300ms.
									//To have longer animation delays, add time to the triggerDelay
	
	var triggerDelay=0;	// You can add more delay to allow the next trigger (in seconds).
	
    $(window).scroll(function(){
        var scrolled=$(window).scrollTop();

        // Reached the top?
        if(scrolled==0){
            at_Top=true;
        }else{
            at_Top=false;
        }

        // Reached the bottom?
        if(scrolled==scrolled_bottom){
            at_Bottom=true;
        }else{
            at_Bottom=false;
        }
        
        // Scroll direction
		if( $(this).scrollTop() > previous_scrolled ){
			scroll_dir=false;  //scroll down
		}else{
			scroll_dir=true;  //scroll up
		}
		
		// Keep previous scrollTop position in memory
		previous_scrolled = $(this).scrollTop();
		
		animationTrigger();
    });

	function animationTrigger(){
        if(at_Top && scroll_dir){
            console.log("Scrolling when at top.");
			$("#wrapper").stop().animate({"margin-top":"3em"},animationDelay);
			setTimeout(function(){
				$("#wrapper").stop().animate({"margin-top":0},animationDelay);
			},animationTimeout);
			clearTimeout(clearConsole);
			var clearConsole = setTimeout(function(){
				console.clear();
			},3000);
        }
        if(at_Bottom && !scroll_dir){
            console.log("Scrolling when at bottom.")
			$("#header").stop().animate({"height":0},animationDelay);
			$("#footer-spacer").stop().animate({"height":"3em"},animationDelay);
			setTimeout(function(){
				$("#header").stop().animate({"height":"3em"},animationDelay);
				$("#footer-spacer").stop().animate({"height":0},animationDelay);
			},animationTimeout);
			clearTimeout(clearConsole);
			var clearConsole = setTimeout(function(){
				console.clear();
			},3000);
        }
    }
	
    // KEYBOARD ARROWS UP/DOWN AND PAGE UP/DOWN SCROLLING
    $(window).on("keydown",function(e){
        //console.log(e.which);
        if( (e.which==38) || (e.which==33) ){    // Arrow up or Page up
            scroll_dir=true;
        }
        if( (e.which==40) || (e.which==34) ){    // Arrow down or Page down
            scroll_dir=false;
        }
		
		// Limit triggers to 1 per second... Because when holding a key down for long, it triggers too fast...
		var thisSecond = new Date().getSeconds()
        if( (triggerTime != thisSecond) || (triggerTime < (thisSecond - triggerDelay) ) ){
            animationTrigger();
            triggerTime=thisSecond;
        }
    })

    // WHEEL SCROLLING
    // Inspired from this SO answer: http://stackoverflow.com/a/7309786/2159528

    //Firefox
    $(window).bind('DOMMouseScroll', function(e){
        var scrolled2=$(window).scrollTop();
        
        if(e.originalEvent.detail > 0) {
            scroll_dir=false;  //scroll down
            //console.log("down");
        }else {
            scroll_dir=true;   //scroll up
            //console.log("up");
        }
        
		// Limit triggers to 1 per second... Because wheel turns quite fast.
        var thisSecond = new Date().getSeconds()
        if( (triggerTime != thisSecond) || (triggerTime < (thisSecond - triggerDelay) ) ){
            animationTrigger();
            triggerTime=thisSecond;
        }
    });

    //IE, Opera, Safari
    $(window).bind('mousewheel', function(e){
		
        if(e.originalEvent.wheelDelta < 0) {
            scroll_dir=false;  //scroll down
        }else {
            scroll_dir=true;   //scroll up
        }
        
        // Limit triggers to 1 per second... Because wheel turns quite fast.
        var thisSecond = new Date().getSeconds()
        if( (triggerTime != thisSecond) || (triggerTime < (thisSecond - triggerDelay) ) ){
            animationTrigger();
            triggerTime=thisSecond;
        }
    });

});	// End Document.ready

body,wrapper{
    padding:0;
    margin:0;
    height:100;
}
#page{
    height:1500px;
    width:100%;
}
#header,#footer{
    height:3em;
    padding:0.5em;
    background-color:cyan;
}
#content{
    height:calc(100% - 8em);    /* -8em for header and footer... (height: 3em + padding: 2x 0,5em) */
    padding:0 0.5em;
    overflow:hidden;
}
#footer-spacer{
    height:0px;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="wrapper">
    <div id="page">
        <div id="header">
            This is the page's top
        </div>
        <div id="content">
            <h1>Scroll this page to see the overscroll effect at top and bottom</h1>
            <br>
            <ul>
                <li>using the mouse wheel</li>
                <li>keyboard arrows</li>
                <li>keyboard page up/down</li>
            </ul>
            <br>
            <br>
            Content...<br>
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        </div>
        
        <div id="footer">
            This is the page's bottom
        </div>
        <div id="footer-spacer"></div>
    </div>
</div>

要在页面位于顶部或底部时检测滚动尝试...
使用它来设置您展示的动画是另一回事。

上层方法:
包装器的 margin 从 0em 动画到 3em，将标题和内容向下推。
所以页面“看起来”像是过度滚动了。

底部方法:
这是一个挑战...
不能使用包装器的 margin-bottom 对顶部做同样的事情，因为它有效……但在视口(viewport)下方，这并不是我们真正想要的。

所以在这种情况下，我将“内容”定义为 height:calc(100% - 8em) (页眉和页脚都有 height:3em和 padding:0.5em) 只是为了确保包装器 100% 填充。要设置动画的空 div 位于页脚 下方...当其高度从 0em 变为 3em 时，它会创建滚动“错觉”将页脚向上推。

请注意，标题同时缩回，以便释放空间。此时， header 不可见，为什么不呢？

当拖动滚动条、旋转鼠标滚轮并按下键盘上4个“常用”键中的1个(箭头和上/下翻页)。

我留下了很多console.log()，你可以用它们来探索它是如何工作的，改进动画，让它成为你的品味。
;)