我的h1不在页面上。
<h1 id="scroll-to">TRIGGER EVENT WHEN SCROLLED TO.</h1>
我想在用户滚动到h1或在浏览器视图中触发警报时触发。
$('#scroll-to').scroll(function() {
alert('you have scrolled to the h1!');
});
我该怎么做呢？
Answers:
您可以计算offset元素的，然后将其与scroll值进行比较，例如：
$(window).scroll(function() {
var hT = $('#scroll-to').offset().top,
hH = $('#scroll-to').outerHeight(),
wH = $(window).height(),
wS = $(this).scrollTop();
if (wS > (hT+hH-wH)){
console.log('H1 on the view!');
}
});
检查这个演示小提琴
更新了Demo Fiddle无提示-而是将FadeIn（）元素
更新了代码，以检查元素是否在视口内。因此，无论您向上滚动还是向下滚动向if语句添加一些规则，此方法都有效：
if (wS > (hT+hH-wH) && (hT > wS) && (wS+wH > hT+hH)){
//Do something
}
.off()解除绑定事件jsfiddle.net/n4pdx/543
当用户滚动到页面的特定部分时，将此问题与jQuery触发操作的最佳答案结合起来
var element_position = $('#scroll-to').offset().top;
$(window).on('scroll', function() {
var y_scroll_pos = window.pageYOffset;
var scroll_pos_test = element_position;
if(y_scroll_pos > scroll_pos_test) {
//do stuff
}
});
更新
我已经改进了代码，以便在元素位于屏幕上方而不是顶部时触发。如果用户点击屏幕底部并且功能尚未触发，它也会触发代码。
var element_position = $('#scroll-to').offset().top;
var screen_height = $(window).height();
var activation_offset = 0.5;//determines how far up the the page the element needs to be before triggering the function
var activation_point = element_position - (screen_height * activation_offset);
var max_scroll_height = $('body').height() - screen_height - 5;//-5 for a little bit of buffer
//Does something when user scrolls to it OR
//Does it when user has reached the bottom of the page and hasn't triggered the function yet
$(window).on('scroll', function() {
var y_scroll_pos = window.pageYOffset;
var element_in_view = y_scroll_pos > activation_point;
var has_reached_bottom_of_page = max_scroll_height <= y_scroll_pos && !element_in_view;
if(element_in_view || has_reached_bottom_of_page) {
//Do something
}
});
我认为您最好的选择是利用可完成此任务的现有库：
http://imakewebthings.com/waypoints/
您可以向元素添加侦听器，当元素到达视口顶部时，监听器将触发：
$('#scroll-to').waypoint(function() {
alert('you have scrolled to the h1!');
});
有关正在使用的惊人演示：
http://tympanus.net/codrops/2013/07/16/on-scroll-header-effects/
Inview库触发了事件，并且与jquery 1.8及更高版本兼容！ https://github.com/protonet/jquery.inview
$('div').on('inview', function (event, visible) {
if (visible == true) {
// element is now visible in the viewport
} else {
// element has gone out of viewport
}
});
阅读此https://remysharp.com/2009/01/26/element-in-view-event-plugin
成功滚动后仅触发一次滚动
可接受的答案对我有用（90％），但我必须对其进行一些调整才能实际触发一次。
$(window).on('scroll',function() {
var hT = $('#comment-box-section').offset().top,
hH = $('#comment-box-section').outerHeight(),
wH = $(window).height(),
wS = $(this).scrollTop();
if (wS > ((hT+hH-wH)-500)){
console.log('comment box section arrived! eh');
// After Stuff
$(window).off('scroll');
doStuff();
}
});
注意：成功滚动是指用户滚动到我的元素时，换句话说，当我的元素在视图中时。
您可以将jQuery插件与inview此类事件结合使用：
jQuery('.your-class-here').one('inview', function (event, visible) {
if (visible == true) {
//Enjoy !
}
});
链接：https : //remysharp.com/2009/01/26/element-in-view-event-plugin
这应该是您所需要的。
Javascript：
$(window).scroll(function() {
var hT = $('#circle').offset().top,
hH = $('#circle').outerHeight(),
wH = $(window).height(),
wS = $(this).scrollTop();
console.log((hT - wH), wS);
if (wS > (hT + hH - wH)) {
$('.count').each(function() {
$(this).prop('Counter', 0).animate({
Counter: $(this).text()
}, {
duration: 900,
easing: 'swing',
step: function(now) {
$(this).text(Math.ceil(now));
}
});
}); {
$('.count').removeClass('count').addClass('counted');
};
}
});
CSS：
#circle
{
width: 100px;
height: 100px;
background: blue;
-moz-border-radius: 50px;
-webkit-border-radius: 50px;
border-radius: 50px;
float:left;
margin:5px;
}
.count, .counted
{
line-height: 100px;
color:white;
margin-left:30px;
font-size:25px;
}
#talkbubble {
width: 120px;
height: 80px;
background: green;
position: relative;
-moz-border-radius: 10px;
-webkit-border-radius: 10px;
border-radius: 10px;
float:left;
margin:20px;
}
#talkbubble:before {
content:"";
position: absolute;
right: 100%;
top: 15px;
width: 0;
height: 0;
border-top: 13px solid transparent;
border-right: 20px solid green;
border-bottom: 13px solid transparent;
}
HTML：
<div id="talkbubble"><span class="count">145</span></div>
<div style="clear:both"></div>
<div id="talkbubble"><span class="count">145</span></div>
<div style="clear:both"></div>
<div id="circle"><span class="count">1234</span></div>
Intersection Observer可能是IMO最好的东西，没有任何外部库，它做得很好。
const options = {
root: null,
threshold: 0.25, // 0 - 1 this work as a trigger.
rootMargin: '150px'
};
const target = document.querySelector('h1#scroll-to');
const observer = new IntersectionObserver(
entries => { // each entry checks if the element is the view or not and if yes trigger the function accordingly
entries.forEach(() => {
alert('you have scrolled to the h1!')
});
}, options);
observer.observe(target);
如果您要基于滚动位置执行许多功能，则完全为此目的构建了滚动魔术（http://scrollmagic.io/）。
它使基于滚动时用户到达特定元素的时间轻松触发JS。它还与GSAP动画引擎（https://greensock.com/）集成，该引擎非常适合视差滚动网站
对于任何处理有时可能超出设备视口范围的元素的人，只需对DaniP的答案进行快速修改即可。
仅添加了一点条件-如果元素大于视口，则当元素的上半部分完全填充视口时，该元素将显示出来。
function elementInView(el) {
// The vertical distance between the top of the page and the top of the element.
var elementOffset = $(el).offset().top;
// The height of the element, including padding and borders.
var elementOuterHeight = $(el).outerHeight();
// Height of the window without margins, padding, borders.
var windowHeight = $(window).height();
// The vertical distance between the top of the page and the top of the viewport.
var scrollOffset = $(this).scrollTop();
if (elementOuterHeight < windowHeight) {
// Element is smaller than viewport.
if (scrollOffset > (elementOffset + elementOuterHeight - windowHeight)) {
// Element is completely inside viewport, reveal the element!
return true;
}
} else {
// Element is larger than the viewport, handle visibility differently.
// Consider it visible as soon as it's top half has filled the viewport.
if (scrollOffset > elementOffset) {
// The top of the viewport has touched the top of the element, reveal the element!
return true;
}
}
return false;
}
我一直使用相同的代码，因此添加了一个简单的jquery插件。480字节长，而且速度很快。在运行时仅分析绑定的元素。
https://www.npmjs.com/package/jquery-on-scrolled-to
这将是
$('#scroll-to').onScrolledTo(0, function() {
alert('you have scrolled to the h1!');
});
或使用0.5而不是0（如果需要在显示一半的h1时发出警报）。