What is lazy loading

Lazy loading is a common front-end optimization technique used to delay loading resources on the page to improve the loading speed and performance of the page. Through lazy loading, it will only be performed when the user needs to access the resource. Load, rather than loading all resources at once. It can be applied to various types of resources, such as pictures, videos, etc. By rationally choosing the implementation method of lazy loading, you can improve the user experience, reduce the load on the server, and thereby improve the performance of the website.

The operating system for this tutorial: Windows 10 system, DELL G3 computer.

Lazy Loading is a common front-end optimization technology that is used to delay loading resources on the page to improve the loading speed and performance of the page. With lazy loading, resources are loaded only when the user needs to access them, rather than loading all resources at once.

In traditional web page loading, when a user opens a web page, all images, videos, scripts and other resources will be loaded at once. This can lead to long page load times, especially for large pages and resource-rich sites. Moreover, if the user does not scroll near the resources that need to be loaded, then these resources will be wasted, causing a great waste of performance.

The principle of lazy loading is to load the corresponding resources when the user scrolls to the visible area. This can effectively reduce page loading time and improve user experience. Lazy loading can be applied to various types of resources such as images, videos, and audios.

There are many ways to implement lazy loading. Here are some common methods:

1. JavaScript-based lazy loading: by listening to scroll events, when an element appears in the visible area , and then load it into the page. You can use the Intersection Observer API to achieve this function, which can monitor the intersection status of elements and the viewport.

2. Lazy loading plug-in based on jQuery: jQuery plug-in such as Lazy Load can easily implement the lazy loading function. By saving the URL of the resource in the data-src attribute, then determining whether the element appears in the visible area during the scroll event, and then assigning the data-src attribute value to the src attribute, lazy loading of images is achieved.

3. CSS-based lazy loading: Use the background-image property of CSS to implement lazy loading of images. First save the URL of the resource in the data-src attribute and then assign it to the element's background-image attribute via JavaScript. When the element enters the visible area, the image is loaded.

Lazy loading can not only improve the loading speed of the page, but also reduce the load on the server. By deferring the loading of resources until users need them, you can reduce unnecessary bandwidth consumption and server requests, thereby improving website performance and responsiveness.

Lazy loading also has some considerations to consider. First, you need to ensure that users will not miss loaded resources when scrolling the page, so the lazy loading threshold needs to be set reasonably. Secondly, it needs to be compatible with browsers that do not support JavaScript, which can be solved by providing an alternative static resource.

In short, lazy loading is an effective front-end optimization technology. By delaying the loading of page resources, the loading speed and performance of the page can be improved. It can be applied to various types of resources, such as pictures, videos, etc. By rationally choosing the implementation method of lazy loading, you can improve the user experience, reduce the load on the server, and thereby improve the performance of the website.

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