window.addEventListener('scroll',function(e){var scrollTop = window.scrollY;if(scrollTop > 0 && scrollTop < articleHeight){title1.classList.add('title-anim');content1.classList.add('content-anim');}else if(scrollTop >= articleHeight && scrollTop < articleHeight*2){title2.classList.add('title-anim');content2.classList.add('content-anim');}else if(scrollTop >= articleHeight*2 && scrollTop < articleHeight*3){title3.classList.add('title-anim2');content3.classList.add('content-anim');}})

<div id="scene_back" class="scene"><img id="pokemon1" src="./img/001.png"><img id="pokemon4" src="./img/004.png"><img id="pokemon7" src="./img/007.png">
</div>
<div id="scene_center" class="scene"><img id="pokemon2" src="./img/002.png"><img id="pokemon5" src="./img/005.png"><img id="pokemon8" src="./img/008.png">
</div>
<div id="scene_front" class="scene"><img id="pokemon3" src="./img/003.png"><img id="pokemon6" src="./img/006.png"><img id="pokemon9" src="./img/009.png">
</div>

var sceneBack = document.getElementById('scene_back'),sceneCenter = document.getElementById('scene_center'),sceneFront = document.getElementById('scene_front');
var old_top1 = 0,old_top2 = 200,old_top3 = 700;addEvent(window,'scroll',onScroll);
onScroll();function onScroll(e){var scrollTop = document.documentElement.scrollTop || document.body.scrollTop;sceneBack.style.top = old_top1+scrollTop*.9+'px';sceneCenter.style.top = old_top2+scrollTop*.7+'px';sceneFront.style.top = old_top3+scrollTop*.3+'px';
}function addEvent(eventTarget, eventType, eventHandler) {if (eventTarget.addEventListener) {eventTarget.addEventListener(eventType, eventHandler, false);} else {if (eventTarget.attachEvent) {eventType = "on" + eventType;eventTarget.attachEvent(eventType, eventHandler);} else {eventTarget["on" + eventType] = eventHandler;}}
}

newTop1 = oldTop1 + scrollTop * x1 ;   (x是个系数)
newTop2 = oldTop2 - scrollTop * x2 ;   (x是个系数)

var sona = document.getElementById('sona'),ahri = document.getElementById('ahri');
var old_top1 = -1000,old_top2 = 1000;addEvent(window,'scroll',onScroll);onScroll();function onScroll(e){var scrollTop = document.documentElement.scrollTop || document.body.scrollTop;sona.style.top = old_top1+scrollTop*2+'px';ahri.style.top = old_top2-scrollTop*0+'px';
}function addEvent(eventTarget, eventType, eventHandler) {if (eventTarget.addEventListener) {eventTarget.addEventListener(eventType, eventHandler, false);} else {if (eventTarget.attachEvent) {eventType = "on" + eventType;eventTarget.attachEvent(eventType, eventHandler);} else {eventTarget["on" + eventType] = eventHandler;}}
}