What are the methods for front-end performance optimization?

Front-end performance optimization methods: 1. Reduce the number of http requests; 2. Image optimization; 3. Use CDN; 4. Turn on GZIP; 5. Optimize style sheets and JS files; 6. Use cookie-free domain names; 7. Optimization of front-end code structure.

Front-end performance optimization method:

1. Reduce the number of http requests

Commonly used to reduce the number of http requests are the following:

1) Merge images. When there are many pictures, they can be merged into one large picture to reduce the number of http requests. Pictures that change frequently may not be suitable, but pictures that change relatively steadily can be considered. In addition to reducing the number of http requests, merging large images can also make full use of caching to improve performance.

2) Merge and compress css style sheets and js scripts. Their common purpose is to reduce the number of http connections.

3) Remove unnecessary requests. Develop invalid request connections remaining after writing code or system upgrade.

4) Make full use of cache. The cache mentioned here is client-side cache or browser cache. The Expires header information is an important basis for client-side caching. The format is similar to Expires:sun, 20 Dec 2017 23:00:00 GMT. If the current time is less than the time specified by Expires, the browser will directly obtain the relevant data information or html file from the cache. If the current time is greater than the time specified by Expires, the browser will send a request to the server to obtain the relevant data information.

Taking Apache as an example, Expires can be set in Apache's configuration file httpd.conf.

2. Image optimization

Optimization method:

1) Use PNG format images as much as possible, which are relatively small in size.

2) For images in different formats, it is best to perform certain optimizations before going online.

3) Delayed loading of images, also called lazy loading.

3. Using CDN

CDN is a content distribution network, which allows users to obtain the content they need nearby, solves network congestion, and improves the response speed of users accessing websites. .

4. Turn on GZIP

GZIP is data compression, which is used to compress all text resources transmitted using the Internet. The method to turn on GZIP is very simple, just go to the corresponding web service configuration file and set it. Taking Apache as an example, add it to the configuration file httpd.conf.

5. Optimization of style sheets and JS files

Generally we will put the css style sheet file at the head of the file. For example, put it in the tag, so that the CSS style sheet can be downloaded as soon as possible. Corresponding to the js script file, generally we put it at the end of the page.

6. Use cookie-free domain names

The concept of cookie-free domain names: When sending a request, you also need to request a static picture and send a cookie. The server will not make any use of these cookies, which means that these cookies are of no use and should not be sent with the request.

7. Optimization of front-end code structure

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