Web App Image Preloading Setup in 2mins

Resource preloading method to speed up web applications. Trust me, this method works and it can be achieved in just 2 minutes. Modern browsers cache the plugin after it loads the resource, so it is actually only used when it is initially loaded (see screenshot below). There will be no longer any problem with slow image loading in web applications! The plugin can also be used to preload other content such as scripts, audio, video, etc... You can also set callback functions for a single project. This will be the content of another article, so stay tuned!

Setting steps

• Includes preload.js plugin
• Create your image loading list
• (optional): Show loading progress bar
• (optional): perform some operations in the load completion callback

Example of code containing progress bar

manifest = [
    "/img/logo.jpg",
    "/assets/image1.jpg",
    "/assets/image2.jpg",
    "/assets/image3.jpg"
    //等等...
];

// 创建一个预加载器。一开始没有向其中添加清单，我们将按需添加项目。
preload = new createjs.LoadQueue(true, ""); // 更改 "" 以添加基本路径

// 显示进度
var $mainProgress = $("#mainProgress"),
    $progressBar = $mainProgress.find('.progress');
$progressBar.width(0);
preload.addEventListener("progress", function() {
    console.log('正在更新预加载进度...'+Math.round(preload.progress*100)+"%");
    $progressBar.width(preload.progress * $mainProgress.width());
});

// 完成回调
preload.addEventListener("complete", function() {
    console.log('资源已预加载...');
});

preload.setMaxConnections(5);
preload.loadManifest(manifest);

Plugin auxiliary code/sample settings

The following resources will help you expand features when you encounter problems:

• PreloadJS / examples / PreloadImages.html – https://www.php.cn/link/91e480d943dda6147aff2bd2dc418c96
• LoadQueue Class API – https://www.php.cn/link/b0a939dc23f32d19bfc5ad11bbfaf093
• Media grid preload – https://www.php.cn/link/fc8956a9c5bb091ed488e75e3df5ae4f

Frequently Asked Questions about Preloading Settings for Web Application Images

What is the purpose of preloading images in web applications?

Image preloading is a technology used in web development that loads images into the browser's cache before they are needed. This is done to improve the user experience by reducing the load time when images are actually needed. When a user accesses a web page, the image is loaded into the cache, making the page load faster and smoother. This is especially useful for websites that contain a lot of graphics and pictures.

How does PHP preloading work in Symfony?

PHP preloading is a feature introduced in PHP 7.4 that allows the server to load PHP files into memory at startup and keep them there for subsequent requests. Symfony supports this feature and can significantly improve performance by reducing I/O operation and compile time. It should be noted that preloading requires opcache to be enabled and is incompatible with certain features such as debugging.

How to preload images without using JavaScript?

There are several ways to preload images without using JavaScript. A common approach is to use CSS. You can use the background-image attribute to load the image in the background of elements not displayed on the page. Another way is to use the HTML link element and set the rel attribute to preload. This will tell the browser to start loading the specified resource as soon as possible.

What is the Symfony WebLink component and what does it have to do with preloading?

The Symfony WebLink component allows you to manage HTTP links for preloading and prefetching resources. It provides a way to add a Link header to an HTTP response. These headers can be used to instruct the browser to preload certain resources, thereby improving the performance of your web application.

What are the potential drawbacks of image preloading?

While image preloading can improve user experience by reducing loading time, it also has some potential drawbacks. It may consume more bandwidth, which can be a problem for users with limited data traffic. It will also increase the initial loading time of the page, as the browser needs to download more data in advance. Therefore, it is important to use this technology with caution and preload only images necessary for the user experience.

How to implement image preloading in my web application?

Implementing image preloading in your web application can be done in a variety of ways. A common approach is to use JavaScript to create new Image objects and set their src attribute to the URL of the image to be preloaded. Another way is to use the HTML link element and set the rel attribute to preload. You can also use CSS to load images in the background of hidden elements.

Can I use image preload with dynamic images?

Yes, you can use image preload with dynamic images. However, this may be more challenging because the URL of the image may be unknown when the page is loading. In this case, you can dynamically add link elements to the document header using JavaScript after the URL is known.

How does image preloading affect SEO?

Image preloading may improve SEO by reducing page loading time, which is a factor that search engines consider when ranking websites. However, it should be noted that preloading should be used with caution and do not attempt to trick search engines by loading content that users cannot see.

Can I use image preload with responsive images?

Yes, you can use image preload with responsive images. However, this may be more complicated, as you may need to preload different versions of the same image for different screen sizes. In this case, you can use the link attribute of the media element to specify the version of the image to be preloaded based on the media query.

How to test the effectiveness of image preloading?

You can test the effectiveness of image preloading by measuring the loading time of web pages with and without preloading. To do this, there are a variety of tools that can be used, such as Google's PageSpeed ​​Insights and Lighthouse. These tools can provide detailed reports on page performance and provide suggestions for improvement.

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