是什么导致无法检测到纯 JavaScript 中 HTML 元素底部的滚动?
What causes this failure to detect scrolling to the bottom of an HTML element in pure JavaScript?
我正在开发纯粹的 JavaScript 无限滚动。
我有一个 post 的 4 列表。当我到达容器底部时,我试图加载更多 posts(“原始”的克隆)。
class InfiniteScroll {
constructor() {
this.observer = null;
this.isLoading = false;
this.postsContainer = document.querySelector('#postsContainer');
this.postsArary = postsContainer.querySelectorAll('.post');
this.hasNextPage = this.postsContainer?.dataset?.hasNextPage === 'true';
this.currentPage = this.postsContainer?.dataset?.currentPage;
this.nextPage = this.hasNextPage ? this.currentPage + 1 : null;
}
loadMorePosts() {
if (this.hasNextPage) {
this.postsArary.forEach(item => {
let postClone = item.cloneNode(true);
this.postsContainer.appendChild(postClone);
});
}
}
bindLoadMoreObserver() {
if (this.postsContainer) {
this.observer = new IntersectionObserver((entries, observer) => {
entries.forEach(entry => {
if (entry && entry.isIntersecting) {
this.loadMorePosts();
}
});
});
this.observer.observe(this.postsContainer);
}
}
init() {
this.bindLoadMoreObserver();
}
}
const infiniteScroll = new InfiniteScroll();
infiniteScroll.init();
body, body * {
margin: 0;
padding: 0;
}
body {
font-family: Arial, Helvetica, sans-serif;
}
.post {
margin: 20px;
padding: 15px;
border: 1px solid #ccc;
border-radius: 5px;
}
p {
line-height: 1.5;
}
<div id="postsContainer" data-has-next-page="true" data-current-page="1" data-max-count="11">
<div class="post">
<h2>Title 1</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Neque dolorum consequatur nostrum sapiente ipsa! Veniam, laudantium accusantium, odio maxime quo adipisci possimus enim quam, voluptate quidem animi perferendis delectus aliquam?</p>
</div>
<div class="post">
<h2>Title 2</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Neque dolorum consequatur nostrum sapiente ipsa! Veniam, laudantium accusantium, odio maxime quo adipisci possimus enim quam, voluptate quidem animi perferendis delectus aliquam?</p>
</div>
<div class="post">
<h2>Title 3</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Neque dolorum consequatur nostrum sapiente ipsa! Veniam, laudantium accusantium, odio maxime quo adipisci possimus enim quam, voluptate quidem animi perferendis delectus aliquam?</p>
</div>
<div class="post">
<h2>Title 4</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Neque dolorum consequatur nostrum sapiente ipsa! Veniam, laudantium accusantium, odio maxime quo adipisci possimus enim quam, voluptate quidem animi perferendis delectus aliquam?</p>
</div>
</div>
问题
post 克隆不是在滚动到最后一个 post 后附加到容器中,而是在页面加载时附加。
我不想用rootMargin
,因为它看起来不太通用
我做错了什么?
好的,也许它会对某人有所帮助:
class InfiniteScroll {
constructor() {
this.observer = null;
this.isLoading = false;
this.postsContainer = document.querySelector('#postsContainer');
this.postsArary = postsContainer.querySelectorAll('.post');
this.hasNextPage = this.postsContainer ? .dataset ? .hasNextPage === 'true';
this.currentPage = this.postsContainer ? .dataset ? .currentPage;
this.nextPage = this.hasNextPage ? this.currentPage + 1 : null;
}
loadMorePosts() {
if (this.hasNextPage) {
this.postsArary.forEach(item => {
let postClone = item.cloneNode(true);
this.postsContainer.appendChild(postClone);
});
} else {
if (this.observer) this.observe.disconnect();
}
}
getLastPost() {
const allPosts = [...this.postsContainer.querySelectorAll('.post')];
return allPosts[allPosts.length - 1];
}
bindLoadMoreObserver() {
if (this.postsContainer) {
this.observer = new IntersectionObserver((entries, observer) => {
entries.forEach(entry => {
if (entry && entry.isIntersecting) {
observer.unobserve(entry.target);
this.loadMorePosts();
observer.observe(this.getLastPost());
}
});
});
this.observer.observe(this.getLastPost());
}
}
init() {
this.bindLoadMoreObserver();
}
}
const infiniteScroll = new InfiniteScroll();
infiniteScroll.init();
我创建了函数 getLastPost
- 它获取了你的最后一个 post(由 js 添加)。
我观察最后一个post,而不是整个容器
然后当这个项目相交时我做了两件事:取消观察当前条目元素,然后在添加新元素之后我观察最后一个 post- 所以这将是最后一个 post, 由js添加。
作为 loadMorePosts 的奖励我看到你想在有下一页时添加 posts 而不是你的 IO 仍然有效,但这不是必需的(性能).所以... disconnect-- disonnect 正在终止 IO 进程也取消观察此 IO 中的所有元素。
带有 perPage
变量和已知帖子总数的示例:
class InfiniteScroll {
constructor() {
this.observer = null;
this.isLoading = false;
this.postsContainer = document.querySelector('#postsContainer');
this.postsArary = postsContainer.querySelectorAll('.post');
this.iterationCount = Number(this.postsContainer.dataset.currentPage);
this.perPage = 5;
this.maxCount = this.postsContainer?.dataset?.maxCount;
this.numberOfPages = Math.ceil(this.maxCount / this.perPage);
this.hasNextPage = this.iterationCount < this.numberOfPages;
}
loadMorePosts() {
if (this.hasNextPage) {
this.postsArary.forEach(item => {
let postClone = item.cloneNode(true);
this.postsContainer.appendChild(postClone);
});
} else {
if (this.observer) this.observer.disconnect();
}
}
getLastPost() {
const allPosts = [...this.postsArary];
return allPosts[allPosts.length - 1];
}
counter() {
if (this.hasNextPage) {
this.iterationCount++;
this.postsContainer.dataset.currentPage = this.iterationCount;
}
this.postsContainer.dataset.hasNextPage = this.hasNextPage;
this.hasNextPage = this.iterationCount < this.numberOfPages;
}
bindLoadMoreObserver() {
if (this.postsContainer) {
this.observer = new IntersectionObserver((entries, observer) => {
entries.forEach(entry => {
if (entry && entry.isIntersecting) {
observer.unobserve(entry.target);
this.counter();
this.loadMorePosts();
observer.observe(this.getLastPost());
}
});
});
this.observer.observe(this.getLastPost());
}
}
init() {
this.bindLoadMoreObserver();
}
}
const infiniteScroll = new InfiniteScroll();
infiniteScroll.init();
body, body * {
margin: 0;
padding: 0;
}
body {
font-family: Arial, Helvetica, sans-serif;
}
.post {
margin: 20px;
padding: 15px;
border: 1px solid #ccc;
border-radius: 5px;
}
p {
line-height: 1.5;
}
<div id="postsContainer" data-has-next-page="true" data-current-page="1" data-max-count="11">
<div class="post">
<h2>Title 1</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Neque dolorum consequatur nostrum sapiente ipsa! Veniam, laudantium accusantium, odio maxime quo adipisci possimus enim quam, voluptate quidem animi perferendis delectus aliquam?</p>
</div>
<div class="post">
<h2>Title 2</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Neque dolorum consequatur nostrum sapiente ipsa! Veniam, laudantium accusantium, odio maxime quo adipisci possimus enim quam, voluptate quidem animi perferendis delectus aliquam?</p>
</div>
<div class="post">
<h2>Title 3</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Neque dolorum consequatur nostrum sapiente ipsa! Veniam, laudantium accusantium, odio maxime quo adipisci possimus enim quam, voluptate quidem animi perferendis delectus aliquam?</p>
</div>
<div class="post">
<h2>Title 4</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Neque dolorum consequatur nostrum sapiente ipsa! Veniam, laudantium accusantium, odio maxime quo adipisci possimus enim quam, voluptate quidem animi perferendis delectus aliquam?</p>
</div>
</div>
我正在开发纯粹的 JavaScript 无限滚动。
我有一个 post 的 4 列表。当我到达容器底部时,我试图加载更多 posts(“原始”的克隆)。
class InfiniteScroll {
constructor() {
this.observer = null;
this.isLoading = false;
this.postsContainer = document.querySelector('#postsContainer');
this.postsArary = postsContainer.querySelectorAll('.post');
this.hasNextPage = this.postsContainer?.dataset?.hasNextPage === 'true';
this.currentPage = this.postsContainer?.dataset?.currentPage;
this.nextPage = this.hasNextPage ? this.currentPage + 1 : null;
}
loadMorePosts() {
if (this.hasNextPage) {
this.postsArary.forEach(item => {
let postClone = item.cloneNode(true);
this.postsContainer.appendChild(postClone);
});
}
}
bindLoadMoreObserver() {
if (this.postsContainer) {
this.observer = new IntersectionObserver((entries, observer) => {
entries.forEach(entry => {
if (entry && entry.isIntersecting) {
this.loadMorePosts();
}
});
});
this.observer.observe(this.postsContainer);
}
}
init() {
this.bindLoadMoreObserver();
}
}
const infiniteScroll = new InfiniteScroll();
infiniteScroll.init();
body, body * {
margin: 0;
padding: 0;
}
body {
font-family: Arial, Helvetica, sans-serif;
}
.post {
margin: 20px;
padding: 15px;
border: 1px solid #ccc;
border-radius: 5px;
}
p {
line-height: 1.5;
}
<div id="postsContainer" data-has-next-page="true" data-current-page="1" data-max-count="11">
<div class="post">
<h2>Title 1</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Neque dolorum consequatur nostrum sapiente ipsa! Veniam, laudantium accusantium, odio maxime quo adipisci possimus enim quam, voluptate quidem animi perferendis delectus aliquam?</p>
</div>
<div class="post">
<h2>Title 2</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Neque dolorum consequatur nostrum sapiente ipsa! Veniam, laudantium accusantium, odio maxime quo adipisci possimus enim quam, voluptate quidem animi perferendis delectus aliquam?</p>
</div>
<div class="post">
<h2>Title 3</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Neque dolorum consequatur nostrum sapiente ipsa! Veniam, laudantium accusantium, odio maxime quo adipisci possimus enim quam, voluptate quidem animi perferendis delectus aliquam?</p>
</div>
<div class="post">
<h2>Title 4</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Neque dolorum consequatur nostrum sapiente ipsa! Veniam, laudantium accusantium, odio maxime quo adipisci possimus enim quam, voluptate quidem animi perferendis delectus aliquam?</p>
</div>
</div>
问题
post 克隆不是在滚动到最后一个 post 后附加到容器中,而是在页面加载时附加。
我不想用rootMargin
,因为它看起来不太通用
我做错了什么?
好的,也许它会对某人有所帮助:
class InfiniteScroll {
constructor() {
this.observer = null;
this.isLoading = false;
this.postsContainer = document.querySelector('#postsContainer');
this.postsArary = postsContainer.querySelectorAll('.post');
this.hasNextPage = this.postsContainer ? .dataset ? .hasNextPage === 'true';
this.currentPage = this.postsContainer ? .dataset ? .currentPage;
this.nextPage = this.hasNextPage ? this.currentPage + 1 : null;
}
loadMorePosts() {
if (this.hasNextPage) {
this.postsArary.forEach(item => {
let postClone = item.cloneNode(true);
this.postsContainer.appendChild(postClone);
});
} else {
if (this.observer) this.observe.disconnect();
}
}
getLastPost() {
const allPosts = [...this.postsContainer.querySelectorAll('.post')];
return allPosts[allPosts.length - 1];
}
bindLoadMoreObserver() {
if (this.postsContainer) {
this.observer = new IntersectionObserver((entries, observer) => {
entries.forEach(entry => {
if (entry && entry.isIntersecting) {
observer.unobserve(entry.target);
this.loadMorePosts();
observer.observe(this.getLastPost());
}
});
});
this.observer.observe(this.getLastPost());
}
}
init() {
this.bindLoadMoreObserver();
}
}
const infiniteScroll = new InfiniteScroll();
infiniteScroll.init();
我创建了函数
getLastPost
- 它获取了你的最后一个 post(由 js 添加)。我观察最后一个post,而不是整个容器
然后当这个项目相交时我做了两件事:取消观察当前条目元素,然后在添加新元素之后我观察最后一个 post- 所以这将是最后一个 post, 由js添加。
作为 loadMorePosts 的奖励我看到你想在有下一页时添加 posts 而不是你的 IO 仍然有效,但这不是必需的(性能).所以... disconnect-- disonnect 正在终止 IO 进程也取消观察此 IO 中的所有元素。
带有 perPage
变量和已知帖子总数的示例:
class InfiniteScroll {
constructor() {
this.observer = null;
this.isLoading = false;
this.postsContainer = document.querySelector('#postsContainer');
this.postsArary = postsContainer.querySelectorAll('.post');
this.iterationCount = Number(this.postsContainer.dataset.currentPage);
this.perPage = 5;
this.maxCount = this.postsContainer?.dataset?.maxCount;
this.numberOfPages = Math.ceil(this.maxCount / this.perPage);
this.hasNextPage = this.iterationCount < this.numberOfPages;
}
loadMorePosts() {
if (this.hasNextPage) {
this.postsArary.forEach(item => {
let postClone = item.cloneNode(true);
this.postsContainer.appendChild(postClone);
});
} else {
if (this.observer) this.observer.disconnect();
}
}
getLastPost() {
const allPosts = [...this.postsArary];
return allPosts[allPosts.length - 1];
}
counter() {
if (this.hasNextPage) {
this.iterationCount++;
this.postsContainer.dataset.currentPage = this.iterationCount;
}
this.postsContainer.dataset.hasNextPage = this.hasNextPage;
this.hasNextPage = this.iterationCount < this.numberOfPages;
}
bindLoadMoreObserver() {
if (this.postsContainer) {
this.observer = new IntersectionObserver((entries, observer) => {
entries.forEach(entry => {
if (entry && entry.isIntersecting) {
observer.unobserve(entry.target);
this.counter();
this.loadMorePosts();
observer.observe(this.getLastPost());
}
});
});
this.observer.observe(this.getLastPost());
}
}
init() {
this.bindLoadMoreObserver();
}
}
const infiniteScroll = new InfiniteScroll();
infiniteScroll.init();
body, body * {
margin: 0;
padding: 0;
}
body {
font-family: Arial, Helvetica, sans-serif;
}
.post {
margin: 20px;
padding: 15px;
border: 1px solid #ccc;
border-radius: 5px;
}
p {
line-height: 1.5;
}
<div id="postsContainer" data-has-next-page="true" data-current-page="1" data-max-count="11">
<div class="post">
<h2>Title 1</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Neque dolorum consequatur nostrum sapiente ipsa! Veniam, laudantium accusantium, odio maxime quo adipisci possimus enim quam, voluptate quidem animi perferendis delectus aliquam?</p>
</div>
<div class="post">
<h2>Title 2</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Neque dolorum consequatur nostrum sapiente ipsa! Veniam, laudantium accusantium, odio maxime quo adipisci possimus enim quam, voluptate quidem animi perferendis delectus aliquam?</p>
</div>
<div class="post">
<h2>Title 3</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Neque dolorum consequatur nostrum sapiente ipsa! Veniam, laudantium accusantium, odio maxime quo adipisci possimus enim quam, voluptate quidem animi perferendis delectus aliquam?</p>
</div>
<div class="post">
<h2>Title 4</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Neque dolorum consequatur nostrum sapiente ipsa! Veniam, laudantium accusantium, odio maxime quo adipisci possimus enim quam, voluptate quidem animi perferendis delectus aliquam?</p>
</div>
</div>