Client rendering (CSR) means that web page content is dynamically generated by the browser by executing JavaScript, rather than the server directly returning the complete HTML. Its core process includes: the browser first downloads the basic HTML file, then requests and executes JS code, and finally JS gets data from the API to fill the page. The advantages of CSR are fast page switching, clear front and back end separation, and suitable for high interactive applications. But the disadvantages are that the first screen is slow loading, difficult SEO optimization, and rely on JS. Suitable for background systems, user dashboards, SPA applications; not suitable for SEO-sensitive, mass marketing or poor network environment scenarios.

When a web page is loading, have you ever encountered a situation where the page content is blank for a few seconds and then suddenly "bounces" out? This is likely to be client-side rendering (CSR for short) that works behind it. It makes web pages look smoother and faster to interact, but it also brings some issues to note.

What is client rendering?

Simply put, client rendering refers to the main content and logic of a web page being generated by the browser running JavaScript on the user device , rather than the server directly returning the complete HTML page. This method makes page switching faster and user experience better because every time you click on a link, you don't need to reload the entire page.

For example, when you use some modern front-end frameworks (such as React and Vue), you will find that the page switching is smooth, the URL has changed but only some of the content has been updated. This is a typical manifestation of CSR.

Client rendering workflow

The core of CSR is that after the browser downloads the HTML file, it requests and executes JavaScript code, and the page content is dynamically generated from these codes. This process can be roughly divided into several steps:

• Download a basic HTML file in the browser
• One or more JS files are referenced in HTML
• Download and execute JS code in the browser
• JS fetches data from the API based on the current URL and populates the data into the page structure

Although this process is flexible, it also comes with a cost: the first load may be slower, because you have to wait for JS to complete before you can see the full content.

Advantages of CSR: Why do you like to use it?

• Fast page switching experience : Once the initial resource is loaded, subsequent page switching only requires partial updates, which is very fast.
• The separation of front and back ends is clearer : the front end is responsible for rendering, and the back end only provides data interfaces for easy team collaboration and maintenance.
• Suitable for highly interactive applications : such as social platforms and online editing tools, such as scenarios that require frequent responses to user operations.

This is also the reason why many modern web applications (such as Gmail, Facebook, and Twitter) use client rendering.

Disadvantages of CSR: Don't ignore these issues

Although client rendering has its advantages, there are several obvious shortcomings:

• The first screen loads slowly : Users may see blank pages or load animations, affecting their first impression.
• SEO optimization is difficult : Search engine crawlers may not catch dynamically generated content unless they are dealt with in particular.
• Depend on JavaScript : If the user's network is poor or JS is disabled, the page may not be displayed normally.

For example, if your website survives on advertising or search traffic, and the homepage is rendered by CSR, then search engines may not see your core content at all, resulting in a decline in ranking.

When should I use CSR?

To choose client rendering or to look at the project type:

• ? Suitable for use of CSR :

  • Internal system and background management interface
  • Personal dashboard after user login
  • Single-page application (SPA) that requires a lot of user interaction

• ?Not suitable for CSR :

  • Marketing page for the public
  • Content-based websites with high SEO requirements
  • Target user groups with poor network environment

If your project belongs to the latter, you can consider server-side rendering (SSR) or static generation (SSG), which can take into account both loading speed and SEO effects.

Basically that's it. Client rendering is not omnipotent or evil. The key is to understand its characteristics and use it in a suitable scenario.

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