Native Infinite Scrolling with the IntersectionObserver API
Feb 17, 2025 am 09:49 AMIntersection Observer API: Efficiently monitor DOM element visibility
Intersection Observer API is an emerging client-side JavaScript API for efficiently monitoring the visibility of specified DOM elements, which is useful for features such as lazy loading, infinite scrolling, and ad visibility.
Browser support and polyfill
This API is relatively new and currently has limited browser support, including Chrome Desktop Edition 51, Chrome Android Edition 51, Android WebView 51, Opera 38 and Opera Android Edition 38. However, a polyfill in development is provided on Github, allowing developers to start using Intersection Observers immediately.
Infinite scrolling implementation guide
This article will provide detailed descriptions on how to use the IntersectionObserver API and polyfill to achieve unlimited scrolling user experience mode, including page settings, script creation, and sentinel element management. The guide contains ES6/ES2015 features such as Promise, template strings, and arrow functions.
Core concept: Sentinel element
The core idea of ??the implementation of infinite scrolling is to use an element at the bottom of the list as a "sentinel", which will trigger more content to be loaded when the browser window approaches the bottom of the page.
Page Settings (HTML)
The page body structure is a simple list:
<ul class="listview"></ul>
To simplify the code, both the initial list items and subsequent pages will be loaded dynamically via JavaScript. We also include polyfill and display the prompt message if the API does not support it:
<div class="polyfill-notice">The polyfill is in use</div> <??>
CSS style is used to set the list view layout and support prompt styles (see the style sheet for details).
Script creation (JavaScript)
First, instantiate a IntersectionObserver
object:
sentinelObserver = new IntersectionObserver(sentinelListener, {threshold: 1});
threshold: 1
means that the event listener will be triggered only when the element is completely within the window. Sentinel elements are marked with orange borders during the demonstration.
Event Listener will perform operations such as removing the current sentinel, setting a load indicator at the bottom of the list, and using the nextPage
method to load the next page. The nextPage
method returns a promise indicating when these operations are completed. After that, we can select the new sentinel element and turn off the load indicator:
sentinelListener = function(entries) { sentinel.unset(); listView.classList.add('loading'); nextPage().then(() => { updateSentinel(); listView.classList.remove('loading'); }); };
updateSentinel
Method Select the new sentinel and select the first element of the newly loaded page:
updateSentinel = function() { sentinel.set(listView.children[listView.children.length - pageSize]); };
The rest of the code mainly implements the nextPage
function. When the Promise returned by loadNextPage()
(simulated network request) is resolved, the provided project object will be rendered into HTML and added to the end of the list.
Further reading
More documentation on API and its principles:
- IntersectionObserver’s Coming into View
- Intersection Observers Explained
- MDN – IntersectionObserver API
Intersection Observer API FAQ
(The FAQ section is omitted here because the original text contains a complete and clear answer.)
The above is the detailed content of Native Infinite Scrolling with the IntersectionObserver API. For more information, please follow other related articles on the PHP Chinese website!

Hot AI Tools

Undress AI Tool
Undress images for free

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics

The following points should be noted when processing dates and time in JavaScript: 1. There are many ways to create Date objects. It is recommended to use ISO format strings to ensure compatibility; 2. Get and set time information can be obtained and set methods, and note that the month starts from 0; 3. Manually formatting dates requires strings, and third-party libraries can also be used; 4. It is recommended to use libraries that support time zones, such as Luxon. Mastering these key points can effectively avoid common mistakes.

PlacingtagsatthebottomofablogpostorwebpageservespracticalpurposesforSEO,userexperience,anddesign.1.IthelpswithSEObyallowingsearchenginestoaccesskeyword-relevanttagswithoutclutteringthemaincontent.2.Itimprovesuserexperiencebykeepingthefocusonthearticl

Event capture and bubble are two stages of event propagation in DOM. Capture is from the top layer to the target element, and bubble is from the target element to the top layer. 1. Event capture is implemented by setting the useCapture parameter of addEventListener to true; 2. Event bubble is the default behavior, useCapture is set to false or omitted; 3. Event propagation can be used to prevent event propagation; 4. Event bubbling supports event delegation to improve dynamic content processing efficiency; 5. Capture can be used to intercept events in advance, such as logging or error processing. Understanding these two phases helps to accurately control the timing and how JavaScript responds to user operations.

If JavaScript applications load slowly and have poor performance, the problem is that the payload is too large. Solutions include: 1. Use code splitting (CodeSplitting), split the large bundle into multiple small files through React.lazy() or build tools, and load it as needed to reduce the first download; 2. Remove unused code (TreeShaking), use the ES6 module mechanism to clear "dead code" to ensure that the introduced libraries support this feature; 3. Compress and merge resource files, enable Gzip/Brotli and Terser to compress JS, reasonably merge files and optimize static resources; 4. Replace heavy-duty dependencies and choose lightweight libraries such as day.js and fetch

The main difference between ES module and CommonJS is the loading method and usage scenario. 1.CommonJS is synchronously loaded, suitable for Node.js server-side environment; 2.ES module is asynchronously loaded, suitable for network environments such as browsers; 3. Syntax, ES module uses import/export and must be located in the top-level scope, while CommonJS uses require/module.exports, which can be called dynamically at runtime; 4.CommonJS is widely used in old versions of Node.js and libraries that rely on it such as Express, while ES modules are suitable for modern front-end frameworks and Node.jsv14; 5. Although it can be mixed, it can easily cause problems.

There are three common ways to initiate HTTP requests in Node.js: use built-in modules, axios, and node-fetch. 1. Use the built-in http/https module without dependencies, which is suitable for basic scenarios, but requires manual processing of data stitching and error monitoring, such as using https.get() to obtain data or send POST requests through .write(); 2.axios is a third-party library based on Promise. It has concise syntax and powerful functions, supports async/await, automatic JSON conversion, interceptor, etc. It is recommended to simplify asynchronous request operations; 3.node-fetch provides a style similar to browser fetch, based on Promise and simple syntax

JavaScript's garbage collection mechanism automatically manages memory through a tag-clearing algorithm to reduce the risk of memory leakage. The engine traverses and marks the active object from the root object, and unmarked is treated as garbage and cleared. For example, when the object is no longer referenced (such as setting the variable to null), it will be released in the next round of recycling. Common causes of memory leaks include: ① Uncleared timers or event listeners; ② References to external variables in closures; ③ Global variables continue to hold a large amount of data. The V8 engine optimizes recycling efficiency through strategies such as generational recycling, incremental marking, parallel/concurrent recycling, and reduces the main thread blocking time. During development, unnecessary global references should be avoided and object associations should be promptly decorated to improve performance and stability.

The difference between var, let and const is scope, promotion and repeated declarations. 1.var is the function scope, with variable promotion, allowing repeated declarations; 2.let is the block-level scope, with temporary dead zones, and repeated declarations are not allowed; 3.const is also the block-level scope, and must be assigned immediately, and cannot be reassigned, but the internal value of the reference type can be modified. Use const first, use let when changing variables, and avoid using var.
