Rsbuild Instance
This section describes all the properties and methods on the Rsbuild instance object.
rsbuild.context
rsbuild.context is a read-only object that provides some context infos.
context.version
The version of @rsbuild/core currently in use.
context.rootPath
The root path of current build, corresponding to the cwd option of createRsbuild method.
context.distPath
The absolute path of the output directory, corresponding to the output.distPath.root config in RsbuildConfig.
When there are multiple environments, Rsbuild will try to get the parent distPath of all environments as context.distPath.
If you want to get the absolute path to the output directory of a specified environment, it is recommended to use environment.distPath.
context.cachePath
The absolute path of the build cache files.
context.devServer
Dev server information, including the current dev server hostname and port number.
type DevServer = {
hostname: string;
port: number;
};
context.bundlerType
The bundler type of current build.
type bundlerType = 'rspack' | 'webpack';
Rsbuild internally supports switching to webpack for comparative testing, so this field is provided for differentiation. Usually, you do not need to use this field.
rsbuild.build
Perform a production mode build.
type BuildOptions = {
/**
* Whether to watch for file changes and rebuild.
* @default false
*/
watch?: boolean;
/**
* Using a custom Rspack Compiler object.
*/
compiler?: Compiler | MultiCompiler;
};
function Build(options?: BuildOptions): Promise<{
/**
* Rspack's [stats](https://rspack.dev/api/javascript-api/stats) object.
*/
stats?: Rspack.Stats | Rspack.MultiStats;
/**
* Stop watching when in watch mode.
*/
close: () => Promise<void>;
}>;
import { logger } from '@rsbuild/core';
// Example 1: run build
await rsbuild.build();
// Example 2: build and handle the error
try {
await rsbuild.build();
} catch (err) {
logger.error('Failed to build.');
logger.error(err);
process.exit(1);
}
// Example 3: build and get all stats
const { stats } = await rsbuild.build();
if (stats) {
const { assets } = stats.toJson({ assets: true });
console.log(assets);
}
Monitor file changes
If you need to watch file changes and re-build, you can set the watch option to true.
await rsbuild.build({
watch: true,
});
In watch mode, the rsbuild.build() returns a close method, which can be used to stop watching:
const result = await rsbuild.build({
watch: true,
});
await result.close();
Stats Object
In non-watch mode, the `rsbuild.build() returns an Rspack stats object:
const result = await rsbuild.build();
console.log(result.stats);
Custom Compiler
In some cases, you may want to use a custom compiler:
import { rspack } from '@rsbuild/core';
const compiler = rspack({
// ...
});
await rsbuild.build({
compiler,
});
rsbuild.startDevServer
Start the local dev server.
type StartDevServerOptions = {
/**
* Using a custom Rspack Compiler object.
*/
compiler?: Compiler | MultiCompiler;
/**
* Whether to get port silently and not print any logs.
* @default false
*/
getPortSilently?: boolean;
};
type StartServerResult = {
urls: string[];
port: number;
server: Server;
};
function StartDevServer(
options?: StartDevServerOptions,
): Promise<StartServerResult>;
Start dev server:
import { logger } from '@rsbuild/core';
// Start dev server
await rsbuild.startDevServer();
// Start dev server and handle the error
try {
await rsbuild.startDevServer();
} catch (err) {
logger.error('Failed to start dev server.');
logger.error(err);
process.exit(1);
}
After successfully starting dev server, you can see the following logs:
➜ Local: http://localhost:3000
➜ Network: http://192.168.0.1:3000
startDevServer returns the following parameters:
urls: URLs to access dev server.port: The actual listening port number.server: Server instance object.
const { urls, port, server } = await rsbuild.startDevServer();
console.log(urls); // ['http://localhost:3000', 'http://192.168.0.1:3000']
console.log(port); // 3000
// Close the dev server
await server.close();
Custom Compiler
In some cases, you may want to use a custom compiler:
import { rspack } from '@rsbuild/core';
const compiler = rspack({
// ...
});
await rsbuild.startDevServer({
compiler,
});
Get Port Silently
In some cases, the default startup port number is already occupied. In this situation, Rsbuild will automatically increment the port number until it finds an available one. This process will output a prompt log. If you do not want this log, you can set getPortSilently to true.
await rsbuild.startDevServer({
getPortSilently: true,
});
rsbuild.createDevServer
Rsbuild comes with a built-in dev server designed to improve the development experience. When you run the rsbuild dev command, the server will start, providing features such as page preview, routing, and hot module reloading.
If you want to integrate Rsbuild dev server into an custom server, you can use this method to get the instance methods of dev server and call them on demand.
type EnvironmentAPI = {
[name: string]: {
/**
* Get stats info about current environment.
*/
getStats: () => Promise<Stats>;
/**
* Load and execute stats bundle in server.
*
* @param entryName - relate to Rsbuild's `source.entry`
* @returns the return value of entry module.
*/
loadBundle: <T = unknown>(entryName: string) => Promise<T>;
/**
* Get the compiled HTML template.
*/
getTransformedHtml: (entryName: string) => Promise<string>;
};
};
type RsbuildDevServer = {
/**
* Listen the Rsbuild server.
* Do not call this method if you are using a custom server.
*/
listen: () => Promise<{
port: number;
urls: string[];
server: {
close: () => Promise<void>;
};
}>;
/**
* Environment API of Rsbuild server.
*/
environments: EnvironmentAPI;
/**
* The resolved port.
* By default, Rsbuild server listens on port `3000` and automatically increments the port number if the port is occupied.
*/
port: number;
/**
* The `connect` app instance.
* Can be used to attach custom middlewares to the dev server.
*/
middlewares: Connect.Server;
/**
* Notify that the Rsbuild server has been started.
* Rsbuild will trigger `onAfterStartDevServer` hook in this stage.
*/
afterListen: () => Promise<void>;
/**
* Activate socket connection.
* This ensures that HMR works properly.
*/
connectWebSocket: (options: { server: HTTPServer }) => void;
/**
* Close the Rsbuild server.
*/
close: () => Promise<void>;
/**
* Print the server URLs.
*/
printUrls: () => void;
/**
* Open URL in the browser after starting the server.
*/
open: () => Promise<void>;
};
type CreateDevServerOptions = {
/**
* Using a custom Rspack Compiler object.
*/
compiler?: Compiler | MultiCompiler;
/**
* Whether to get port silently and not print any logs.
* @default false
*/
getPortSilently?: boolean;
/**
* Whether to trigger Rsbuild compilation
* @default true
*/
runCompile?: boolean;
};
function CreateDevServer(
options?: CreateDevServerOptions,
): Promise<RsbuildDevServer>;
Here is an example with express:
import { createRsbuild } from '@rsbuild/core';
import express from 'express';
export async function startDevServer() {
// Init Rsbuild
const rsbuild = await createRsbuild({});
const app = express();
// Create Rsbuild DevServer instance
const rsbuildServer = await rsbuild.createDevServer();
// Apply Rsbuild’s built-in middlewares
app.use(rsbuildServer.middlewares);
const httpServer = app.listen(rsbuildServer.port, async () => {
// Notify Rsbuild that the custom server has started
await rsbuildServer.afterListen();
});
rsbuildServer.connectWebSocket({ server: httpServer });
}
For detailed usage, please refer to: Example.
If you want to use Rsbuild DevServer to start the project directly, you can use the Rsbuild - startDevServer method directly. startDevServer is actually syntactic sugar for the following code:
const server = await rsbuild.createDevServer();
await server.listen();
connectWebSocket
Rsbuild has a builtin WebSocket handler to support HMR:
- When a user accesses a page through browser, a WebSocket connection request is automatically initiated to the server.
- After the Rsbuild dev server detects the connection request, it instructs the builtin WebSocket handler to process it.
- After the browser successfully establishes a connection with the Rsbuild WebSocket handler, real-time communication is possible.
- The Rsbuild WebSocket handler notifies the browser after each recompilation is complete. The browser then sends a
hot-update.(js|json) request to the dev server to load the new compiled module.
When you use custom server, you may encounter HMR connection error problems. This is because the custom server does not forward WebSocket connection requests to Rsbuild's WebSocket handler.
At this time, you need to use the connectWebSocket method to enable Rsbuild to sense and process the WebSocket connection request from the browser.
const rsbuildServer = await rsbuild.createDevServer();
const httpServer = app.listen(rsbuildServer.port);
rsbuildServer.connectWebSocket({ server: httpServer });
rsbuild.preview
Start a server to preview the production build locally. This method should be executed after rsbuild.build.
type PreviewOptions = {
/**
* Whether to get port silently
* @default false
*/
getPortSilently?: boolean;
/**
* Whether to check if the dist directory exists and is not empty.
* @default true
*/
checkDistDir?: boolean;
};
type StartServerResult = {
urls: string[];
port: number;
server: {
close: () => Promise<void>;
};
};
function preview(options?: PreviewOptions): Promise<StartServerResult>;
Start the server:
import { logger } from '@rsbuild/core';
// Start preview server
await rsbuild.preview();
// Start preview server and handle the error
try {
await rsbuild.preview();
} catch (err) {
logger.error('Failed to start preview server.');
logger.error(err);
process.exit(1);
}
preview returns the following parameters:
urls: URLs to access server.port: The actual listening port number.server: Server instance object.
const { urls, port, server } = await rsbuild.preview();
console.log(urls); // ['http://localhost:3000', 'http://192.168.0.1:3000']
console.log(port); // 3000
// Close the server
await server.close();
rsbuild.createCompiler
Create an Rspack Compiler instance. If there are multiple environments for this build, the return value is MultiCompiler.
function CreateCompiler(): Promise<Compiler | MultiCompiler>;
const compiler = await rsbuild.createCompiler();
You do not need to use this API unless you need to custom the dev server or other advanced scenarios.
rsbuild.addPlugins
Register one or more Rsbuild plugins, which can be called multiple times.
This method needs to be called before compiling. If it is called after compiling, it will not affect the compilation result.
type AddPluginsOptions = { before?: string; environment?: string };
function AddPlugins(
plugins: Array<RsbuildPlugin | Falsy>,
options?: AddPluginsOptions,
): void;
rsbuild.addPlugins([pluginFoo(), pluginBar()]);
// Insert before the bar plugin
rsbuild.addPlugins([pluginFoo()], { before: 'bar' });
// Add plugin for node environment
rsbuild.addPlugins([pluginFoo()], { environment: 'node' });
rsbuild.getPlugins
Get all the Rsbuild plugins registered in the current Rsbuild instance.
function GetPlugins(): RsbuildPlugin[];
console.log(rsbuild.getPlugins());
rsbuild.removePlugins
Removes one or more Rsbuild plugins, which can be called multiple times.
This method needs to be called before compiling. If it is called after compiling, it will not affect the compilation result.
function RemovePlugins(pluginNames: string[]): void;
// add plugin
const pluginFoo = pluginFoo();
rsbuild.addPlugins(pluginFoo);
// remove plugin
rsbuild.removePlugins([pluginFoo.name]);
rsbuild.isPluginExists
Determines whether a plugin has been registered.
function IsPluginExists(pluginName: string): boolean;
rsbuild.addPlugins([pluginFoo()]);
rsbuild.isPluginExists(pluginFoo().name); // true
rsbuild.initConfigs
The initConfigs method is used to initialize the internal configs of Rsbuild and return the Rspack config generated internally by Rsbuild.
Usually, you do not need to call the initConfigs method, because it will be automatically called when methods such as rsbuild.build, rsbuild.startDevServer are called.
function InitConfigs(): Promise<{
rspackConfigs: Rspack.Configuration[];
}>;
const { rspackConfigs } = await rsbuild.initConfigs();
console.log(rspackConfigs);
rsbuild.inspectConfig
The inspectConfig method is typically used for debugging the internal configuration of Rsbuild. It returns the internally generated Rsbuild config and Rspack config, serializes them into strings, and supports writing them to the disk.
If you need to view the Rsbuild and Rspack configurations during the build process, you can use debug mode, or obtain them through hooks such as onBeforeBuild, onBeforeCreateCompile.
type InspectConfigOptions = {
// View the config in the specified environment
// defaults to "development", can be set to "production"
mode?: RsbuildMode;
// Whether to enable verbose mode, display the complete content of the function in the config
// defaults to `false`
verbose?: boolean;
// Specify the output path
// defaults to the value of `output.distPath.root`
outputPath?: string;
// Whether to write the result to disk
// defaults to `false`
writeToDisk?: boolean;
};
async function InspectConfig(options?: InspectConfigOptions): Promise<{
rsbuildConfig: string;
bundlerConfigs: string[];
environmentConfigs: string[];
origin: {
rsbuildConfig: RsbuildConfig;
environmentConfigs: Record<string, EnvironmentConfig>;
bundlerConfigs: BundlerConfigs[];
};
}>;
Example
Get the content of configs in string format:
const { rsbuildConfig, bundlerConfigs } = await rsbuild.inspectConfig();
console.log(rsbuildConfig, bundlerConfigs);
Write the config content to disk:
await rsbuild.inspectConfig({
writeToDisk: true,
});
Output Path
You can set the output path using outputPath. The default value is output.distPath.root.
If outputPath is a relative path, it will be concatenated relative to the value of output.distPath.root. You can also set outputPath to an absolute path, in which case the files will be written directly to that path. For example:
import path from 'node:path';
await rsbuild.inspectConfig({
writeToDisk: true,
outputPath: path.join(__dirname, 'custom-dir'),
});
rsbuild.onBeforeCreateCompiler
onBeforeCreateCompiler is a callback function that is triggered after the Compiler instance has been created, but before the build process begins. This hook is called when you run rsbuild.startDevServer, rsbuild.build, or rsbuild.createCompiler.
You can access the Rspack configuration array through the bundlerConfigs parameter. The array may contain one or more Rspack configurations. It depends on whether multiple environments are configured.
function OnBeforeCreateCompiler(
callback: (params: {
bundlerConfigs: Rspack.Configuration[];
environments: Record<string, EnvironmentContext>;
}) => Promise<void> | void,
): void;
rsbuild.onBeforeCreateCompiler(({ bundlerConfigs }) => {
console.log('the Rspack config is ', bundlerConfigs);
});
rsbuild.onAfterCreateCompiler
onAfterCreateCompiler is a callback function that is triggered after the compiler instance has been created, but before the build process. This hook is called when you run rsbuild.startDevServer, rsbuild.build, or rsbuild.createCompiler.
You can access the Compiler instance through the compiler parameter:
function OnAfterCreateCompiler(callback: (params: {
compiler: Compiler | MultiCompiler;
environments: Record<string, EnvironmentContext>;
}) => Promise<void> | void;): void;
rsbuild.onAfterCreateCompiler(({ compiler }) => {
console.log('the compiler is ', compiler);
});
rsbuild.onBeforeBuild
onBeforeBuild is a callback function that is triggered before the production build is executed.
You can access the Rspack configuration array through the bundlerConfigs parameter. The array may contain one or more Rspack configurations. It depends on whether multiple environments are configured.
Moreover, you can use isWatch to determine whether it is watch mode, and use isFirstCompile to determine whether it is the first build on watch mode.
function OnBeforeBuild(
callback: (params: {
isWatch: boolean;
isFirstCompile: boolean;
bundlerConfigs?: Rspack.Configuration[];
environments: Record<string, EnvironmentContext>;
}) => Promise<void> | void,
): void;
rsbuild.onBeforeBuild(({ bundlerConfigs }) => {
console.log('the Rspack config is ', bundlerConfigs);
});
rsbuild.onAfterBuild
onAfterBuild is a callback function that is triggered after running the production build. You can access the build result information via the stats parameter.
Moreover, you can use isWatch to determine whether it is watch mode, and use isFirstCompile to determine whether it is the first build on watch mode.
function OnAfterBuild(
callback: (params: {
isFirstCompile: boolean;
isWatch: boolean;
stats?: Stats | MultiStats;
environments: Record<string, EnvironmentContext>;
}) => Promise<void> | void,
): void;
rsbuild.onAfterBuild(({ stats }) => {
console.log(stats?.toJson());
});
rsbuild.onCloseBuild
Called when closing the build instance. Can be used to perform cleanup operations when the building is closed.
Rsbuild CLI will automatically call this hook after running rsbuild build, while users of the JavaScript API need to manually call the rsbuild.close() method to trigger this hook.
function onCloseBuild(callback: () => Promise<void> | void): void;
rsbuild.onCloseBuild(async () => {
console.log('close build!');
});
rsbuild.onBeforeStartDevServer
Called before starting the dev server.
function OnBeforeStartDevServer(
callback: (params: {
environments: Record<string, EnvironmentContext>;
}) => Promise<void> | void,
): void;
rsbuild.onBeforeStartDevServer(() => {
console.log('before start!');
});
rsbuild.onAfterStartDevServer
Called after starting the dev server, you can get the port number with the port parameter, and the page routes info with the routes parameter.
type Routes = Array<{
entryName: string;
pathname: string;
}>;
function OnAfterStartDevServer(
callback: (params: {
port: number;
routes: Routes;
environments: Record<string, EnvironmentContext>;
}) => Promise<void> | void,
): void;
rsbuild.onAfterStartDevServer(({ port, routes }) => {
console.log('this port is: ', port);
console.log('this routes is: ', routes);
});
rsbuild.onCloseDevServer
Called when closing the dev server. Can be used to perform cleanup operations when the dev server is closed.
function onCloseDevServer(callback: () => Promise<void> | void): void;
rsbuild.onCloseDevServer(async () => {
console.log('close dev server!');
});
rsbuild.onBeforeStartProdServer
Called before starting the production preview server.
function OnBeforeStartProdServer(callback: () => Promise<void> | void): void;
rsbuild.onBeforeStartProdServer(() => {
console.log('before start!');
});
rsbuild.onAfterStartProdServer
Called after starting the production preview server, you can get the port number with the port parameter, and the page routes info with the routes parameter.
type Routes = Array<{
entryName: string;
pathname: string;
}>;
function OnAfterStartProdServer(
callback: (params: {
port: number;
routes: Routes;
environments: Record<string, EnvironmentContext>;
}) => Promise<void> | void,
): void;
rsbuild.onAfterStartProdServer(({ port, routes }) => {
console.log('this port is: ', port);
console.log('this routes is: ', routes);
});
rsbuild.onDevCompileDone
Called after each development mode build, you can use isFirstCompile to determine whether it is the first build.
function OnDevCompileDone(
callback: (params: {
isFirstCompile: boolean;
stats: Stats | MultiStats;
environments: Record<string, EnvironmentContext>;
}) => Promise<void> | void,
): void;
rsbuild.onDevCompileDone(({ isFirstCompile }) => {
if (isFirstCompile) {
console.log('first compile!');
} else {
console.log('re-compile!');
}
});
rsbuild.onExit
Called when the process is going to exit, this hook can only execute synchronous code.
function OnExit(callback: () => void): void;
rsbuild.onExit(() => {
console.log('exit!');
});
rsbuild.getRsbuildConfig
Get the Rsbuild config, this method must be called after the modifyRsbuildConfig hook is executed.
type GetRsbuildConfig = {
(): Readonly<RsbuildConfig>;
(type: 'original' | 'current'): Readonly<RsbuildConfig>;
(type: 'normalized'): NormalizedConfig;
};
You can specify the type of Rsbuild config to read by using the type parameter:
// Get the original Rsbuild config defined by the user.
getRsbuildConfig('original');
// Get the current Rsbuild config.
// The content of this config will change at different execution stages of Rsbuild.
// For example, the content of the current Rsbuild config will be modified after running the `modifyRsbuildConfig` hook.
getRsbuildConfig('current');
// Get the normalized Rsbuild config.
// This method must be called after the `modifyRsbuildConfig` hook has been executed.
// It is equivalent to the `getNormalizedConfig` method.
getRsbuildConfig('normalized');
rsbuild.onBeforeBuild(() => {
const config = rsbuild.getRsbuildConfig();
console.log(config.html?.title);
});
rsbuild.getNormalizedConfig
Get the all normalized Rsbuild config or the Rsbuild config of a specified environment, this method must be called after the modifyRsbuildConfig hook is executed.
Compared with the api.getRsbuildConfig method, the config returned by this method has been normalized, and the type definition of the config will be narrowed. For example, the undefined type of config.html will be removed.
It is recommended to use this method to get the Rsbuild config.
/** Get the Rsbuild configuration of the specified environment */
function GetNormalizedConfig(options: {
environment: string;
}): Readonly<NormalizedEnvironmentConfig>;
/** Get all Rsbuild configurations */
function GetNormalizedConfig(): Readonly<NormalizedConfig>;
rsbuild.onBeforeBuild(() => {
const config = api.getNormalizedConfig();
console.log(config.html.title);
});
