[英]Enable scrolling event when div is in viewport only once then reset when out of viewport
我试图跟踪每次以Amplitude进入视口的元素。 现在,当元素滚动到视图中时,jQuery会检测元素ID(如果元素是向上滚动还是向下滚动),并指出它是滚动事件。 这些项目显示在振幅管理中。 问题是,当div在视口中时,每次鼠标滚动都会触发滚动事件。 因此,当视口中每个元素仅需要一个事件时,它将创建大量事件。 如何仅触发一次事件,然后再次将其重置为不在视口中?
function isScrolledIntoView(elem) {
// set offset by 10%
var offSet = jQuery(window).height()*0.1;
// offset scrolltop
var docViewTop = jQuery(window).scrollTop() + offSet;
// set window height area to 80%
var windowSize = jQuery(window).height()*0.8;
var docViewBottom = docViewTop + windowSize;
var elemTop = jQuery(elem).offset().top;
var elemBottom = elemTop + jQuery(elem).height();
return ((elemBottom <= docViewBottom) && (elemTop >= docViewTop));
}
var lastScrollTop = 0;
jQuery(window).scroll(function (event) {
// detects scroll direction.
var st = jQuery(this).scrollTop();
if (st > lastScrollTop){
var action = 'ScrollDown';
} else {
var action = 'ScrollUp';
}
lastScrollTop = st;
jQuery('.trackScrolling').each(function () {
// get element ID
var elementID = jQuery(this).attr("id");
var ScrollEvents = 'ScrollEvents';
// if in viewport fire event
if (isScrolledIntoView(this) === true) {
gu_event(ScrollEvents, action, elementID);
}
});
});
您需要为每个元素创建一个布尔标志,以检查它是否已经在视口中,并添加另一个if
条件检查它,如下所示:
var elements = [];
var lastScrollTop = 0;
jQuery('.trackScrolling').each(function () {
elements.push({
"elem": this,
"id": jQuery(this).attr("id")),
"inView": false
});
});
function isScrolledIntoView(elem) {
// set offset by 10%
var offSet = jQuery(window).height()*0.1;
// offset scrolltop
var docViewTop = jQuery(window).scrollTop() + offSet;
// set window height area to 80%
var windowSize = jQuery(window).height()*0.8;
var docViewBottom = docViewTop + windowSize;
var elemTop = jQuery(elem).offset().top;
var elemBottom = elemTop + jQuery(elem).height();
return ((elemBottom <= docViewBottom) && (elemTop >= docViewTop));
}
jQuery(window).scroll(function (event) {
var action;
// detects scroll direction.
var st = jQuery(this).scrollTop();
if (st > lastScrollTop){
action = 'ScrollDown';
} else {
action = 'ScrollUp';
}
lastScrollTop = st;
for (var i = 0; i < elements.length; i++) {
var ScrollEvents = 'ScrollEvents';
if (elements[i].inView === true && isScrolledIntoView(elements[i].elem) === true) {
// do nothing in this case...
console.log('Element ' + elements[i].id + ' is already in view!');
} else if (isScrolledIntoView(elements[i].elem) === true) {
// set the flag in this case and send the event
elements[i].inView = true;
gu_event(ScrollEvents, action, elements[i].id);
} else if (isScrolledIntoView(elements[i].elem) === false) {
// reset the flag in this case
elements[i].inView = false;
}
}
});
我没有在scroll
功能中不断查找所有.trackScrolling
元素,而是预先存储了对它们的引用-每个元素的ID以及它是否在视口中都存储在一个对象中。
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