我有一个div，只有300像素大，我希望它在页面加载时滚动到内容的底部。这个div有动态添加的内容，需要一直向下滚动。现在如果用户决定向上滚动，我不希望它跳回底部，直到用户再次向下滚动
是否有可能有一个div，将保持滚动到底部，除非用户向上滚动，当用户滚动回底部时，它需要保持自己在底部，即使添加了新的动态内容。我该怎么做呢。
当前回答
我发现最友好的解决方案是将滚动-快照-对齐方法与少量Javascript结合起来。前一种解决方案本身的问题是，抓拍太强了，你必须滚动很远才能摆脱它。
相反，我们可以在容器滚动到底部时使用捕捉动态，然后在用户向上滚动超过某个阈值时禁用它。
这个解决方案还有一个额外的好处，那就是它是一个渐进的增强:如果用户禁用了Javascript，它就会退回到只使用css的方法。
const container = document.getElementById("container"); const snap = document.getElementById("snap"); // Scroll the view to the bottom once initially container.scrollTop = container.scrollHeight; container.addEventListener("scroll", (event) => { const target = event.currentTarget; const scroll = target.scrollTop; const maxScroll = target.scrollHeight - target.clientHeight; const threshold = 50; // px isScrollBottomedOut = maxScroll - scroll < threshold; // If the user scrolls up more than the threshold, disable snapping // If the user scrolls down again, reenable snapping snap.style.display = isScrollBottomedOut ? "block" : "none"; }); #container { width: 200px; height: 500px; overflow-y: auto; overflow-x: hidden; -webkit-overflow-scrolling: touch; -ms-scroll-chaining: none; overscroll-behavior: contain; -ms-scroll-snap-type: y proximity; scroll-snap-type: y proximity; border: 2px solid black; } #snap { scroll-snap-align: end; } <div id="container"> <ol> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> <li>item</li> </ol> <!-- This is the snapping target, if visible --> <div id="snap"></div> </div>
其他回答
这个问题有原生的支持。
有一个叫做*. scrollintoview的方法。 在运行此方法一次之后，它将容器滚动保持在底部。 即使在容器中添加了新内容，它也会滚动到底部。
import {
AfterViewInit,
Directive,
ElementRef,
} from '@angular/core';
@Directive({
selector: '[aeScrollIntoView]',
})
export class ScrollIntoViewDirective implements AfterViewInit {
constructor(private readonly el: ElementRef<HTMLDivElement>) {}
ngAfterViewInit(): void {
this.el.nativeElement.scrollIntoView({ behavior: 'smooth' });
}
}
<div aeScrollIntoView>
Your long and dynamic content.
Whenever new content is added to this container, it scrolls to the bottom.
<div>
与Bootstrap 5:
< span style=" font - family:宋体;max-height: 300 px;" > < div > <！——你这里的内容——> < / div > < / div >
以下是你所需要的(我尽了最大的努力，一路上进行了大量的谷歌搜索):
<html>
<head>
<script>
// no jquery, or other craziness. just
// straight up vanilla javascript functions
// to scroll a div's content to the bottom
// if the user has not scrolled up. Includes
// a clickable "alert" for when "content" is
// changed.
// this should work for any kind of content
// be it images, or links, or plain text
// simply "append" the new element to the
// div, and this will handle the rest as
// proscribed.
let scrolled = false; // at bottom?
let scrolling = false; // scrolling in next msg?
let listener = false; // does element have content changed listener?
let contentChanged = false; // kind of obvious
let alerted = false; // less obvious
function innerHTMLChanged() {
// this is here in case we want to
// customize what goes on in here.
// for now, just:
contentChanged = true;
}
function scrollToBottom(id) {
if (!id) { id = "scrollable_element"; }
let DEBUG = 0; // change to 1 and open console
let dstr = "";
let e = document.getElementById(id);
if (e) {
if (!listener) {
dstr += "content changed listener not active\n";
e.addEventListener("DOMSubtreeModified", innerHTMLChanged);
listener = true;
} else {
dstr += "content changed listener active\n";
}
let height = (e.scrollHeight - e.offsetHeight); // this isn't perfect
let offset = (e.offsetHeight - e.clientHeight); // and does this fix it? seems to...
let scrollMax = height + offset;
dstr += "offsetHeight: " + e.offsetHeight + "\n";
dstr += "clientHeight: " + e.clientHeight + "\n";
dstr += "scrollHeight: " + e.scrollHeight + "\n";
dstr += "scrollTop: " + e.scrollTop + "\n";
dstr += "scrollMax: " + scrollMax + "\n";
dstr += "offset: " + offset + "\n";
dstr += "height: " + height + "\n";
dstr += "contentChanged: " + contentChanged + "\n";
if (!scrolled && !scrolling) {
dstr += "user has not scrolled\n";
if (e.scrollTop != scrollMax) {
dstr += "scroll not at bottom\n";
e.scroll({
top: scrollMax,
left: 0,
behavior: "auto"
})
e.scrollTop = scrollMax;
scrolling = true;
} else {
if (alerted) {
dstr += "alert exists\n";
} else {
dstr += "alert does not exist\n";
}
if (contentChanged) { contentChanged = false; }
}
} else {
dstr += "user scrolled away from bottom\n";
if (!scrolling) {
dstr += "not auto-scrolling\n";
if (e.scrollTop >= scrollMax) {
dstr += "scroll at bottom\n";
scrolled = false;
if (alerted) {
dstr += "alert exists\n";
let n = document.getElementById("alert");
n.remove();
alerted = false;
contentChanged = false;
scrolled = false;
}
} else {
dstr += "scroll not at bottom\n";
if (contentChanged) {
dstr += "content changed\n";
if (!alerted) {
dstr += "alert not displaying\n";
let n = document.createElement("div");
e.append(n);
n.id = "alert";
n.style.position = "absolute";
n.classList.add("normal-panel");
n.classList.add("clickable");
n.classList.add("blink");
n.innerHTML = "new content!";
let nposy = parseFloat(getComputedStyle(e).height) + 18;
let nposx = 18 + (parseFloat(getComputedStyle(e).width) / 2) - (parseFloat(getComputedStyle(n).width) / 2);
dstr += "nposx: " + nposx + "\n";
dstr += "nposy: " + nposy + "\n";
n.style.left = nposx;
n.style.top = nposy;
n.addEventListener("click", () => {
dstr += "clearing alert\n";
scrolled = false;
alerted = false;
contentChanged = false;
n.remove();
});
alerted = true;
} else {
dstr += "alert already displayed\n";
}
} else {
alerted = false;
}
}
} else {
dstr += "auto-scrolling\n";
if (e.scrollTop >= scrollMax) {
dstr += "done scrolling";
scrolling = false;
scrolled = false;
} else {
dstr += "still scrolling...\n";
}
}
}
}
if (DEBUG && dstr) console.log("stb:\n" + dstr);
setTimeout(() => { scrollToBottom(id); }, 50);
}
function scrollMessages(id) {
if (!id) { id = "scrollable_element"; }
let DEBUG = 1;
let dstr = "";
if (scrolled) {
dstr += "already scrolled";
} else {
dstr += "got scrolled";
scrolled = true;
}
dstr += "\n";
if (contentChanged && alerted) {
dstr += "content changed, and alerted\n";
let n = document.getElementById("alert");
if (n) {
dstr += "alert div exists\n";
let e = document.getElementById(id);
let nposy = parseFloat(getComputedStyle(e).height) + 18;
dstr += "nposy: " + nposy + "\n";
n.style.top = nposy;
} else {
dstr += "alert div does not exist!\n";
}
} else {
dstr += "content NOT changed, and not alerted";
}
if (DEBUG && dstr) console.log("sm: " + dstr);
}
setTimeout(() => { scrollToBottom("messages"); }, 1000);
/////////////////////
// HELPER FUNCTION
// simulates adding dynamic content to "chat" div
let count = 0;
function addContent() {
let e = document.getElementById("messages");
if (e) {
let br = document.createElement("br");
e.append("test " + count);
e.append(br);
count++;
}
}
</script>
<style>
button {
border-radius: 5px;
}
#container {
padding: 5px;
}
#messages {
background-color: blue;
border: 1px inset black;
border-radius: 3px;
color: white;
padding: 5px;
overflow-x: none;
overflow-y: auto;
max-height: 100px;
width: 100px;
margin-bottom: 5px;
text-align: left;
}
.bordered {
border: 1px solid black;
border-radius: 5px;
}
.inline-block {
display: inline-block;
}
.centered {
text-align: center;
}
.normal-panel {
background-color: #888888;
border: 1px solid black;
border-radius: 5px;
padding: 2px;
}
.clickable {
cursor: pointer;
}
</style>
</head>
<body>
<div id="container" class="bordered inline-block centered">
<div class="inline-block">My Chat</div>
<div id="messages" onscroll="scrollMessages('messages')">
test<br>
test<br>
test<br>
test<br>
test<br>
test<br>
test<br>
test<br>
test<br>
test<br>
</div>
<button onclick="addContent();">Add Content</button>
</div>
</body>
</html>
注意:你可能需要在scrollToBottom和scrollMessages中调整警报位置(nposx和nposy)来匹配你的需求…
还有一个链接到我自己的工作示例，托管在我的服务器上:https://night-stand.ca/jaretts_tests/chat_scroll.html
我刚刚实现了这个，也许你可以用我的方法。
假设我们有以下HTML:
<div id="out" style="overflow:auto"></div>
然后我们可以检查它是否滚动到底部:
var out = document.getElementById("out");
// allow 1px inaccuracy by adding 1
var isScrolledToBottom = out.scrollHeight - out.clientHeight <= out.scrollTop + 1;
scrollHeight gives you the height of the element, including any non visible area due to overflow. clientHeight gives you the CSS height or said in another way, the actual height of the element. Both methods returns the height without margin, so you needn't worry about that. scrollTop gives you the position of the vertical scroll. 0 is top and max is the scrollHeight of the element minus the element height itself. When using the scrollbar it can be difficult (it was in Chrome for me) to get the scrollbar all the way down to the bottom. so I threw in a 1px inaccuracy. So isScrolledToBottom will be true even if the scrollbar is 1px from the bottom. You can set this to whatever feels right to you.
然后，只需将元素的scrollTop设置为底部即可。
if(isScrolledToBottom)
out.scrollTop = out.scrollHeight - out.clientHeight;
我已经为你做了一个小提琴的概念:http://jsfiddle.net/dotnetCarpenter/KpM5j/
编辑: 增加了代码片段以澄清当isScrolledToBottom为真时。
Stick scrollbar to bottom const out = document.getElementById("out") let c = 0 setInterval(function() { // allow 1px inaccuracy by adding 1 const isScrolledToBottom = out.scrollHeight - out.clientHeight <= out.scrollTop + 1 const newElement = document.createElement("div") newElement.textContent = format(c++, 'Bottom position:', out.scrollHeight - out.clientHeight, 'Scroll position:', out.scrollTop) out.appendChild(newElement) // scroll to bottom if isScrolledToBottom is true if (isScrolledToBottom) { out.scrollTop = out.scrollHeight - out.clientHeight } }, 500) function format () { return Array.prototype.slice.call(arguments).join(' ') } #out { height: 100px; } <div id="out" style="overflow:auto"></div> <p>To be clear: We want the scrollbar to stick to the bottom if we have scrolled all the way down. If we scroll up, then we don't want the content to move. </p>
以下是我的做法。div的高度是650px。我决定如果滚动高度在底部的150px范围内，那么自动滚动它。否则，留给用户。
if (container_block.scrollHeight - container_block.scrollTop < 800) {
container_block.scrollTo(0, container_block.scrollHeight);
}
