Hello, everyone. I'm Carson. the following React component code uses three use keywords. Do you understand their role? 'use client' function App() { using data = use(ctx); // ... } it is true that I haven't written React for several days, and I can't even understand the grammar. This article will talk about the respective meanings of these use keywords. use client begins with the 'use client' declaration at the top of the code, which is used in a manner similar to the strict mode declaration: 'use strict'; // here is the JavaScript code in strict mode The 'use client' declaration is defined in the RSC ( React Server Component , server-side component) protocol. the React application of RSC is enabled. All components are rendered on the server by default (you can experience it through Next v13 ). Only component files that declare 'use client' are rendered at the front end. suppose our React application component structure is as follows, where red represents server component , blue represents client component (declare 'use client' ): then when the application is packaged, the D and E components will be packaged into separate files. On the front end, React can render A, B, C components directly. But for D and E, you need to request back the component code in the form of JSONP before rendering. using keyword then comes the using keyword before the data variable: using data = use(ctx); The using keyword is proposed by tc39 proposal ECMAScript Explicit Resource Management , and is used to provide unified lifecycle management (when…