How to implement lazy loading for image resources to improve page loading speed?
When a web page contains a large number of image resources, implementing lazy loading can effectively improve page loading speed. The core principle is to delay loading images outside the viewport and only load the resources when the user scrolls to the relevant area. Native attribute: Use the HTML5 loading="lazy" attribute, directly added to the `<img>` tag (e.g., `<img src="image.jpg" loading="lazy">`). The browser will automatically determine the image position and delay loading, with compatibility covering modern mainstream browsers. JavaScript implementation: Monitor the intersection state between image elements and the viewport through the Intersection Observer API. When the image enters the viewport, assign the value of data-src (or other custom attributes) to the src attribute to achieve loading. This is suitable for scenarios requiring custom loading logic. Third-party libraries: Integrate lightweight lazy loading libraries (such as LazyLoad.js, lozad.js) to handle edge cases (e.g., compatibility with older browsers, preloading distance settings) and reduce development complexity. It is recommended to prioritize the native loading attribute to improve basic performance, and combine Intersection Observer or third-party libraries for complex scenarios. At the same time, set width and height attributes for images to avoid layout shifts, and cooperate with image compression and CDN acceleration to further optimize the loading experience.
