html {scroll-behavior: smooth;
}

例如：
<a href="#top"><div id="one">点我回到顶部</div>
</a>

document.querySelector('回到顶部按钮').onclick = () => { scrollTo(0, 0) }

function smoothScrollToTop() {window.scrollTo({left: 0,top: 0,behavior: 'smooth'})
}
document.getElementById('回到顶部按钮').onclick = smoothScrollToTop;

element.scrollIntoView({behavior: 'auto | smooth | auto(default)',block: 'start | center | end | nearest (default)'
})

function smoothScrollToTop() {document.getElementById("top").scrollIntoView({ block: "start", behavior: "smooth" })
}
document.getElementById("scrollToTopButton").onclick = smoothScrollToTop;
//top就是最顶部元素地id，scrollToTopButton就是回到顶部按钮地id

//setInterval版
function smoothScrollToTop() {let smoothScrollToTopSetInterval = setInterval(() => {let Y_TopValve = (window.pageYOffset || document.body.scrollTop || document.documentElement.scrollTop);if (Y_TopValve > 1) {scrollTo(0, Math.floor(Y_TopValve * 0.85));} else {scrollTo(0, 0);clearInterval(smoothScrollToTopSetInterval);}}, 1000 / 60)
}document.getElementById('回到顶部按钮').onclick = smoothScrollToTop;

//setTimeout版
function fnScroll() {let Y_TopValve = (window.pageYOffset || document.body.scrollTop || document.documentElement.scrollTop);if (Y_TopValve > 1) {scrollTo(0, Math.floor(Y_TopValve * 0.85));} else {scrollTo(0, 0);}
}
function smoothScrollToTop() {setTimeout(() => {fnScroll();let Y_TopValve = (window.pageYOffset || document.body.scrollTop || document.documentElement.scrollTop);if (Y_TopValve > 0) {smoothScrollToTop();}}, 1000 / 60);
}
document.getElementById('回到顶部按钮').onclick = smoothScrollToTop;

function smoothScrollToTop() {let Y_TopValve = (window.pageYOffset || document.body.scrollTop || document.documentElement.scrollTop);if (Y_TopValve > 1) {window.requestAnimationFrame(smoothScrollToTop);scrollTo(0, Math.floor(Y_TopValve * 0.85));} else {scrollTo(0, 0);}
}
document.getElementById('回到顶部按钮').onclick = smoothScrollToTop;