Front-end performance optimization methods

Front-end performance optimization methods include: 1. Reduce the number of http requests; 2. Move the script back to reduce the impact on concurrent downloads; 3. Avoid frequent DOM operations; 4. Compress images; 5. Pass CSS selectors allow browsers to parse from right to left to improve efficiency, etc.

Front-end performance optimization methods include: reducing the number of http requests; moving the script back to reduce the impact on concurrent downloads; avoiding frequent DOM operations; compressing images ;Use CSS selectors to make the browser parse from right to left to improve efficiency

The content contained in the front end is rich, including HTML, CSS, JS, images and other various resources . Therefore, front-end optimization is complex and necessary. Next, I will introduce the method of front-end performance optimization in this article, which has a certain reference effect and I hope it will be helpful to everyone.

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Purpose of optimization

The purpose of optimization is to make the page load faster, respond more promptly to user operations, and bring a better user experience to users. For developers, optimization can reduce the number of page requests and save money. resource.

There are many methods of front-end optimization, which can be divided into two categories. The first category is page-level optimization such as the number of http requests, the location optimization of inline scripts, etc., and the second category is code-level optimization. Optimization, such as DOM operation optimization, CSS selector optimization, image optimization and HTML structure optimization in Javascript, etc.

Page level optimization

Number of http requests

Reducing the number of http requests is the most important and most effective method. Use the following methods to reduce http requests

(1) Set up the http cache reasonably. Proper cache settings can greatly reduce http requests. Try to make resources stay in the cache as long as possible

(2) Simplify the page from the design and implementation level. It is most direct to keep the page simple and reduce the use of resources.

(3) Resource merging and compression, merge external scripts and styles as much as possible, and merge multiple into one.

(4) CSS Sprites, by merging CSS images, this is a good way to reduce the number of requests

Location of inline scripts

Browsers make concurrent requests, but external link scripts often block other resources when loading. For example, before the script is loaded, the images, styles and other scripts behind it are blocked until the script is loaded. Start loading. If the script is placed in a relatively high position, it will affect the loading speed of the entire page and thus affect the user experience. Therefore, move the script as far back as possible to reduce the impact on concurrent downloads

Code-level optimization

DOM operation optimization:

To avoid frequent DOM operations directly on the document, you can use classname instead of a large number of inline style modifications. For complex UI elements, set position to absolute or fixed, try to use css animation, and use canvas appropriately as much as possible. Reduce the use of css expressions and use event agents

Image optimization

Optimize front-end performance by compressing images

CSS selector:

Most people think that browsers parse CSS from left to right. In fact, parsing from right to left is more efficient because the first An id selection basically limits the scope of the search.

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