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Script using Intersection Observer API
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function setObserver(targetElementsClassName) { | |
// vars for Intersection Observer as scroll event | |
const ObserverObj = { | |
previousY: 0, | |
previousRatio: 0, | |
loadCount: 0, | |
taegetElements: d3.selectAll(targetElementsClassName), | |
loadMax: ObserverObj.taegetElements.size(), | |
} | |
// main | |
ObserverObj.taegetElements.each(function (_, i) { | |
const target = d3.select(this); | |
// create IntersectionObserver object to return callback | |
const observer = new IntersectionObserver(function (entries) { | |
entries.forEach(function (entry) { | |
const currentY = entry.boundingClientRect.top; | |
const currentRatio = entry.intersectionRatio; | |
const isIntersecting = entry.isIntersecting; | |
if (ObserverObj.loadCount === ObserverObj.loadMax) { | |
if (currentY < ObserverObj.previousY) { | |
if (currentRatio > ObserverObj.previousRatio && isIntersecting) { | |
// down enter | |
console.log('down enter'); | |
} else { | |
// down leave | |
console.log('down leave'); | |
} | |
} else if (currentY > ObserverObj.previousY) { | |
if (isIntersecting) { | |
// up leave | |
console.log('up leave'); | |
} else { | |
// up enter | |
console.log('up enter'); | |
} | |
} | |
} else { | |
ObserverObj.loadCount = ObserverObj.loadCount + 1; | |
} | |
}); | |
}); | |
// observe target element | |
const options = { | |
root: null, | |
rootMargin: '0', | |
threshold: 0 | |
} | |
observer.observe(target.node(), options); | |
}); | |
} | |
// usage | |
setObserver(".box"); |
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