实现思路：利用粘性定位sticky，以及滚动事件实现。首先我们应该设置滚动动画开始位置和结束位置 ，然后根据位置计算透明度或者transform，scale的值。

 首先根据上述图线计算属性值，代码如下：

function createAnimate(scrollStart, scrollEnd, valueStart, valueEnd) {return function (x) {if (x < scrollStart) {return valueStart;}if (x > scrollEnd) {return valueEnd;}const bili = (valueEnd - valueStart) / (scrollEnd - scrollStart);return bili * (x - scrollStart) + valueStart;};}

然后考虑到每个dom它的动画不是只有一个属性可能有多个，例如scale,opacity,transform等。然后应该将dom和属性存储到map集合中，key为dom,属性为value。

const items = document.querySelectorAll('.list-item');
const animationMap = new Map();const getTitleAnimation = (scrollStart, scrollEnd, dom) => {const opacityAnimation = createAnimate(scrollStart, scrollEnd, 1, 0);const yAnimation = createAnimate(scrollStart, scrollEnd, 0, -200);const transform = function (x) {return `translate(0,${yAnimation(x)}px)`;};const opacity = function (x) {return opacityAnimation(x);};return {transform,opacity,};};const updateMap=()=>{for (const item of items) {animationMap.set(item,getTitleAnimation(scrollStart + 50, scrollEnd, item));}
}

然后就是属性赋值：

const updateStyles = () => {const scrollY = window.scrollY;for (const [dom, animations] of animationMap) {for (const prop in animations) {const value = animations[prop](scrollY);dom.style[prop] = value;}}};
updateStyles();
window.addEventListener('scroll', updateStyles);

全部代码访问： liuzicheng/web - Gitee.com