Questions frequently asked by front-end interviewers: How to optimize web page loading speed?

Optimizing web page loading speed has always been a crucial part of front-end development. During interviews, interviewers often ask questions about web page loading speed optimization, because this not only tests the interviewer's understanding of front-end performance optimization, but also reflects his problem-solving ability and practical experience. Here are some common methods and tips on how to optimize web page loading speed for your reference.

1. Reduce HTTP requests

1. Merge files: Merge multiple CSS files into one and multiple JavaScript files into one to reduce the number of HTTP requests.
2. Use CSS sprites: combine the small icons used on the website into one image, and display different icons by setting background-position to reduce the number of requests.

2. Compress files

1. Compress images: Use image compression tools such as TinyPNG, ImageOptim, etc. to compress images to an appropriate size and reduce file size.
2. Use compression tools: compress HTML, CSS, JavaScript, remove unnecessary content such as spaces and comments, and reduce file size.

3. Use CDN

1. Place static resources such as images, style sheets, scripts, etc. on CDN to speed up file loading.
2. Utilize no-cache parameters: Add timestamp parameters or hash parameters when referencing external resources to avoid caching problems.

4. Delayed loading

1. Lazy loading of images: Delay the loading of images on the page until the user scrolls the page, reducing the pressure during initial loading.
2. Loading on demand: Use require.js, webpack and other tools to load JavaScript modules on demand to reduce the loading volume of the first screen.

5. Optimize CSS and JavaScript

1. Put CSS in the head and JavaScript at the bottom of the body to avoid render-blocking.
2. Reduce DOM operations: Reduce frequent operations on the DOM, try to operate in memory and then render to the page at once.
3. Avoid using too many CSS styles, simplify the style sheet structure as much as possible, and reduce the file size.

6. Cache

1. Set cache headers: Control the cache strategy and reduce requests for server resources by setting response headers such as Cache-Control and Expires.
2. Use localStorage or sessionStorage: Store some static data locally to reduce requests for server resources.

The above are some common methods and techniques for optimizing web page loading speed. I hope they can help you answer related questions better during interviews. With the continuous development of technology, the methods of optimizing web page loading speed are also constantly updated, so you need to continue to learn and practice to continuously improve your front-end performance optimization capabilities.

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