Bun's fast native bundler is now in beta. It can be used via the bun build
CLI command or the Bun.build()
JavaScript API.
await Bun.build({
entrypoints: ['./index.tsx'],
outdir: './build',
});
bun build ./index.tsx --outdir ./build
It's fast. The numbers below represent performance on esbuild's three.js benchmark.
Why bundle?
The bundler is a key piece of infrastructure in the JavaScript ecosystem. As a brief overview of why bundling is so important:
- Reducing HTTP requests. A single package in
node_modules
may consist of hundreds of files, and large applications may have dozens of such dependencies. Loading each of these files with a separate HTTP request becomes untenable very quickly, so bundlers are used to convert our application source code into a smaller number of self-contained "bundles" that can be loaded with a single request. - Code transforms. Modern apps are commonly built with languages or tools like TypeScript, JSX, and CSS modules, all of which must be converted into plain JavaScript and CSS before they can be consumed by a browser. The bundler is the natural place to configure these transformations.
- Framework features. Frameworks rely on bundler plugins & code transformations to implement common patterns like file-system routing, client-server code co-location (think
getServerSideProps
or Remix loaders), and server components.
Let's jump into the bundler API.
Note that the Bun bundler is not intended to replace tsc
for typechecking or generating type declarations.
Basic example
Let's build our first bundle. You have the following two files, which implement a simple client-side rendered React app.
import * as ReactDOM from 'react-dom/client';
import {Component} from "./Component"
const root = ReactDOM.createRoot(document.getElementById('root')!);
root.render(<Component message="Sup!" />)
export function Component(props: {message: string}) {
return <p>{props.message}</p>
}
Here, index.tsx
is the "entrypoint" to our application. Commonly, this will be a script that performs some side effect, like starting a server or—in this case—initializing a React root. Because we're using TypeScript & JSX, we need to bundle our code before it can be sent to the browser.
To create our bundle:
await Bun.build({
entrypoints: ['./index.tsx'],
outdir: './out',
})
bun build ./index.tsx --outdir ./out
For each file specified in entrypoints
, Bun will generate a new bundle. This bundle will be written to disk in the ./out
directory (as resolved from the current working directory). After running the build, the file system looks like this:
.
├── index.tsx
├── Component.tsx
└── out
└── index.js
The contents of out/index.js
will look something like this:
// ...
// ~20k lines of code
// including the contents of `react-dom/client` and all its dependencies
// this is where the $jsxDEV and $createRoot functions are defined
// Component.tsx
function Component(props) {
return $jsxDEV("p", {
children: props.message
}, undefined, false, undefined, this);
}
// index.tsx
var rootNode = document.getElementById("root");
var root = $createRoot(rootNode);
root.render($jsxDEV(Component, {
message: "Sup!"
}, undefined, false, undefined, this));
Tutorial: Run this file in your browser
Watch mode
Like the runtime and test runner, the bundler supports watch mode natively.
bun build ./index.tsx --outdir ./out --watch
Content types
Like the Bun runtime, the bundler supports an array of file types out of the box. The following table breaks down the bundler's set of standard "loaders". Refer to Bundler > File types for full documentation.
Extensions | Details |
---|---|
.js .jsx , .cjs .mjs .mts .cts .ts .tsx | Uses Bun's built-in transpiler to parse the file and transpile TypeScript/JSX syntax to vanilla JavaScript. The bundler executes a set of default transforms including dead code elimination and tree shaking. At the moment Bun does not attempt to down-convert syntax; if you use recently ECMAScript syntax, that will be reflected in the bundled code. |
| JSON files are parsed and inlined into the bundle as a JavaScript object.
|
| TOML files are parsed and inlined into the bundle as a JavaScript object.
|
| The contents of the text file are read and inlined into the bundle as a string.
|
.node .wasm | These files are supported by the Bun runtime, but during bundling they are treated as assets. |
Assets
If the bundler encounters an import with an unrecognized extension, it treats the imported file as an external file. The referenced file is copied as-is into outdir
, and the import is resolved as a path to the file.
// bundle entrypoint
import logo from "./logo.svg";
console.log(logo);
// bundled output
var logo = "./logo-ab237dfe.svg";
console.log(logo);
The exact behavior of the file loader is also impacted by naming
and publicPath
.
Refer to the Bundler > Loaders page for more complete documentation on the file loader.
Plugins
The behavior described in this table can be overridden or extended with plugins. Refer to the Bundler > Loaders page for complete documentation.
API
entrypoints
Required. An array of paths corresponding to the entrypoints of our application. One bundle will be generated for each entrypoint.
const result = await Bun.build({
entrypoints: ["./index.ts"],
});
// => { success: boolean, outputs: BuildArtifact[], logs: BuildMessage[] }
bun build --entrypoints ./index.ts
# the bundle will be printed to stdout
# <bundled code>
outdir
The directory where output files will be written.
const result = await Bun.build({
entrypoints: ['./index.ts'],
outdir: './out'
});
// => { success: boolean, outputs: BuildArtifact[], logs: BuildMessage[] }
bun build --entrypoints ./index.ts --outdir ./out
# a summary of bundled files will be printed to stdout
If outdir
is not passed to the JavaScript API, bundled code will not be written to disk. Bundled files are returned in an array of BuildArtifact
objects. These objects are Blobs with extra properties; see Outputs for complete documentation.
const result = await Bun.build({
entrypoints: ["./index.ts"],
});
for (const res of result.outputs) {
// Can be consumed as blobs
await res.text();
// Bun will set Content-Type and Etag headers
new Response(res);
// Can be written manually, but you should use `outdir` in this case.
Bun.write(path.join("out", res.path), res);
}
When outdir
is set, the path
property on a BuildArtifact
will be the absolute path to where it was written to.
target
The intended execution environment for the bundle.
await Bun.build({
entrypoints: ['./index.ts'],
outdir: './out',
target: 'browser', // default
})
bun build --entrypoints ./index.ts --outdir ./out --target browser
Depending on the target, Bun will apply different module resolution rules and optimizations.
browser | Default. For generating bundles that are intended for execution by a browser. Prioritizes the "browser" export condition when resolving imports. Importing any built-in modules, like node:events or node:path will work, but calling some functions, like fs.readFile will not work. |
| For generating bundles that are intended to be run by the Bun runtime. In many cases, it isn't necessary to bundle server-side code; you can directly execute the source code without modification. However, bundling your server code can reduce startup times and improve running performance. All bundles generated with If any entrypoints contains a Bun shebang ( When using |
node | For generating bundles that are intended to be run by Node.js. Prioritizes the "node" export condition when resolving imports, and outputs .mjs . In the future, this will automatically polyfill the Bun global and other built-in bun:* modules, though this is not yet implemented. |
format
Specifies the module format to be used in the generated bundles.
Bun defaults to "esm"
, and provides experimental support for "cjs"
and "iife"
.
format: "esm"
- ES Module
This is the default format, which supports ES Module syntax including top-level await
, import.meta, and more.
await Bun.build({
entrypoints: ['./index.tsx'],
outdir: './out',
format: "esm",
})
bun build ./index.tsx --outdir ./out --format esm
To use ES Module syntax in browsers, set format
to "esm"
and make sure your <script type="module">
tag has type="module"
set.
format: "cjs"
- CommonJS
To build a CommonJS module, set format
to "cjs"
. When choosing "cjs"
, the default target changes from "browser"
(esm) to "node"
(cjs). CommonJS modules transpiled with format: "cjs", target: "node"
can be executed in both Bun and Node.js (assuming the APIs in use are supported by both).
await Bun.build({
entrypoints: ['./index.tsx'],
outdir: './out',
format: "cjs",
})
bun build ./index.tsx --outdir ./out --format cjs
format: "iife"
- IIFE
TODO: document IIFE once we support globalNames.
splitting
Whether to enable code splitting.
await Bun.build({
entrypoints: ['./index.tsx'],
outdir: './out',
splitting: false, // default
})
bun build ./index.tsx --outdir ./out --splitting
When true
, the bundler will enable code splitting. When multiple entrypoints both import the same file, module, or set of files/modules, it's often useful to split the shared code into a separate bundle. This shared bundle is known as a chunk. Consider the following files:
import { shared } from './shared.ts';
import { shared } from './shared.ts';
export const shared = 'shared';
To bundle entry-a.ts
and entry-b.ts
with code-splitting enabled:
await Bun.build({
entrypoints: ['./entry-a.ts', './entry-b.ts'],
outdir: './out',
splitting: true,
})
bun build ./entry-a.ts ./entry-b.ts --outdir ./out --splitting
Running this build will result in the following files:
.
├── entry-a.tsx
├── entry-b.tsx
├── shared.tsx
└── out
├── entry-a.js
├── entry-b.js
└── chunk-2fce6291bf86559d.js
The generated chunk-2fce6291bf86559d.js
file contains the shared code. To avoid collisions, the file name automatically includes a content hash by default. This can be customized with naming
.
plugins
A list of plugins to use during bundling.
await Bun.build({
entrypoints: ['./index.tsx'],
outdir: './out',
plugins: [/* ... */],
})
n/a
Bun implements a universal plugin system for both Bun's runtime and bundler. Refer to the plugin documentation for complete documentation.
env
Controls how environment variables are handled during bundling. Internally, this uses define
to inject environment variables into the bundle, but makes it easier to specify the environment variables to inject.
env: "inline"
Injects environment variables into the bundled output by converting process.env.FOO
references to string literals containing the actual environment variable values.
await Bun.build({
entrypoints: ['./index.tsx'],
outdir: './out',
env: "inline",
})
FOO=bar BAZ=123 bun build ./index.tsx --outdir ./out --env inline
For the input below:
console.log(process.env.FOO);
console.log(process.env.BAZ);
The generated bundle will contain the following code:
console.log("bar");
console.log("123");
env: "PUBLIC_*"
(prefix)
Inlines environment variables matching the given prefix (the part before the *
character), replacing process.env.FOO
with the actual environment variable value. This is useful for selectively inlining environment variables for things like public-facing URLs or client-side tokens, without worrying about injecting private credentials into output bundles.
await Bun.build({
entrypoints: ['./index.tsx'],
outdir: './out',
// Inline all env vars that start with "ACME_PUBLIC_"
env: "ACME_PUBLIC_*",
})
FOO=bar BAZ=123 ACME_PUBLIC_URL=https://acme.com bun build ./index.tsx --outdir ./out --env 'ACME_PUBLIC_*'
For example, given the following environment variables:
FOO=bar BAZ=123 ACME_PUBLIC_URL=https://acme.com
And source code:
console.log(process.env.FOO);
console.log(process.env.ACME_PUBLIC_URL);
console.log(process.env.BAZ);
The generated bundle will contain the following code:
console.log(process.env.FOO);
console.log("https://acme.com");
console.log(process.env.BAZ);
env: "disable"
Disables environment variable injection entirely.
For example, given the following environment variables:
FOO=bar BAZ=123 ACME_PUBLIC_URL=https://acme.com
And source code:
console.log(process.env.FOO);
console.log(process.env.ACME_PUBLIC_URL);
console.log(process.env.BAZ);
The generated bundle will contain the following code:
console.log(process.env.FOO);
console.log(process.env.BAZ);
sourcemap
Specifies the type of sourcemap to generate.
await Bun.build({
entrypoints: ['./index.tsx'],
outdir: './out',
sourcemap: 'linked', // default 'none'
})
bun build ./index.tsx --outdir ./out --sourcemap=linked
"none" | Default. No sourcemap is generated. |
| A separate
|
"external" | A separate *.js.map file is created alongside each *.js bundle without inserting a //# sourceMappingURL comment. |
Generated bundles contain a debug id that can be used to associate a bundle with its corresponding sourcemap. This debugId
is added as a comment at the bottom of the file.
// <generated bundle code>
//# debugId=<DEBUG ID>
"inline"
A sourcemap is generated and appended to the end of the generated bundle as a base64 payload.
// <bundled code here> //# sourceMappingURL=data:application/json;base64,<encoded sourcemap here>
The associated
*.js.map
sourcemap will be a JSON file containing an equivalentdebugId
property.
minify
Whether to enable minification. Default false
.
When targeting bun
, identifiers will be minified by default.
To enable all minification options:
await Bun.build({
entrypoints: ['./index.tsx'],
outdir: './out',
minify: true, // default false
})
bun build ./index.tsx --outdir ./out --minify
To granularly enable certain minifications:
await Bun.build({
entrypoints: ['./index.tsx'],
outdir: './out',
minify: {
whitespace: true,
identifiers: true,
syntax: true,
},
})
bun build ./index.tsx --outdir ./out --minify-whitespace --minify-identifiers --minify-syntax
external
A list of import paths to consider external. Defaults to []
.
await Bun.build({
entrypoints: ['./index.tsx'],
outdir: './out',
external: ["lodash", "react"], // default: []
})
bun build ./index.tsx --outdir ./out --external lodash --external react
An external import is one that will not be included in the final bundle. Instead, the import
statement will be left as-is, to be resolved at runtime.
For instance, consider the following entrypoint file:
import _ from "lodash";
import {z} from "zod";
const value = z.string().parse("Hello world!")
console.log(_.upperCase(value));
Normally, bundling index.tsx
would generate a bundle containing the entire source code of the "zod"
package. If instead, we want to leave the import
statement as-is, we can mark it as external:
await Bun.build({
entrypoints: ['./index.tsx'],
outdir: './out',
external: ['zod'],
})
bun build ./index.tsx --outdir ./out --external zod
The generated bundle will look something like this:
import {z} from "zod";
// ...
// the contents of the "lodash" package
// including the `_.upperCase` function
var value = z.string().parse("Hello world!")
console.log(_.upperCase(value));
To mark all imports as external, use the wildcard *
:
await Bun.build({
entrypoints: ['./index.tsx'],
outdir: './out',
external: ['*'],
})
bun build ./index.tsx --outdir ./out --external '*'
packages
Control whatever package dependencies are included to bundle or not. Possible values: bundle
(default), external
. Bun treats any import which path do not start with .
, ..
or /
as package.
await Bun.build({
entrypoints: ['./index.ts'],
packages: 'external',
})
bun build ./index.ts --packages external
naming
Customizes the generated file names. Defaults to ./[dir]/[name].[ext]
.
await Bun.build({
entrypoints: ['./index.tsx'],
outdir: './out',
naming: "[dir]/[name].[ext]", // default
})
bun build ./index.tsx --outdir ./out --entry-naming [dir]/[name].[ext]
By default, the names of the generated bundles are based on the name of the associated entrypoint.
.
├── index.tsx
└── out
└── index.js
With multiple entrypoints, the generated file hierarchy will reflect the directory structure of the entrypoints.
.
├── index.tsx
└── nested
└── index.tsx
└── out
├── index.js
└── nested
└── index.js
The names and locations of the generated files can be customized with the naming
field. This field accepts a template string that is used to generate the filenames for all bundles corresponding to entrypoints. where the following tokens are replaced with their corresponding values:
[name]
- The name of the entrypoint file, without the extension.[ext]
- The extension of the generated bundle.[hash]
- A hash of the bundle contents.[dir]
- The relative path from the project root to the parent directory of the source file.
For example:
Token | [name] | [ext] | [hash] | [dir] |
---|---|---|---|---|
./index.tsx | index | js | a1b2c3d4 | "" (empty string) |
./nested/entry.ts | entry | js | c3d4e5f6 | "nested" |
We can combine these tokens to create a template string. For instance, to include the hash in the generated bundle names:
await Bun.build({
entrypoints: ['./index.tsx'],
outdir: './out',
naming: 'files/[dir]/[name]-[hash].[ext]',
})
bun build ./index.tsx --outdir ./out --entry-naming [name]-[hash].[ext]
This build would result in the following file structure:
.
├── index.tsx
└── out
└── files
└── index-a1b2c3d4.js
When a string
is provided for the naming
field, it is used only for bundles that correspond to entrypoints. The names of chunks and copied assets are not affected. Using the JavaScript API, separate template strings can be specified for each type of generated file.
await Bun.build({
entrypoints: ['./index.tsx'],
outdir: './out',
naming: {
// default values
entry: '[dir]/[name].[ext]',
chunk: '[name]-[hash].[ext]',
asset: '[name]-[hash].[ext]',
},
})
bun build ./index.tsx --outdir ./out --entry-naming "[dir]/[name].[ext]" --chunk-naming "[name]-[hash].[ext]" --asset-naming "[name]-[hash].[ext]"
root
The root directory of the project.
await Bun.build({
entrypoints: ['./pages/a.tsx', './pages/b.tsx'],
outdir: './out',
root: '.',
})
n/a
If unspecified, it is computed to be the first common ancestor of all entrypoint files. Consider the following file structure:
.
└── pages
└── index.tsx
└── settings.tsx
We can build both entrypoints in the pages
directory:
await Bun.build({
entrypoints: ['./pages/index.tsx', './pages/settings.tsx'],
outdir: './out',
})
bun build ./pages/index.tsx ./pages/settings.tsx --outdir ./out
This would result in a file structure like this:
.
└── pages
└── index.tsx
└── settings.tsx
└── out
└── index.js
└── settings.js
Since the pages
directory is the first common ancestor of the entrypoint files, it is considered the project root. This means that the generated bundles live at the top level of the out
directory; there is no out/pages
directory.
This behavior can be overridden by specifying the root
option:
await Bun.build({
entrypoints: ['./pages/index.tsx', './pages/settings.tsx'],
outdir: './out',
root: '.',
})
bun build ./pages/index.tsx ./pages/settings.tsx --outdir ./out --root .
By specifying .
as root
, the generated file structure will look like this:
.
└── pages
└── index.tsx
└── settings.tsx
└── out
└── pages
└── index.js
└── settings.js
publicPath
A prefix to be appended to any import paths in bundled code.
In many cases, generated bundles will contain no import
statements. After all, the goal of bundling is to combine all of the code into a single file. However there are a number of cases with the generated bundles will contain import
statements.
- Asset imports — When importing an unrecognized file type like
*.svg
, the bundler defers to thefile
loader, which copies the file intooutdir
as is. The import is converted into a variable - External modules — Files and modules can be marked as
external
, in which case they will not be included in the bundle. Instead, theimport
statement will be left in the final bundle. - Chunking. When
splitting
is enabled, the bundler may generate separate "chunk" files that represent code that is shared among multiple entrypoints.
In any of these cases, the final bundles may contain paths to other files. By default these imports are relative. Here is an example of a simple asset import:
import logo from './logo.svg';
console.log(logo);
// logo.svg is copied into <outdir>
// and hash is added to the filename to prevent collisions
var logo = './logo-a7305bdef.svg';
console.log(logo);
Setting publicPath
will prefix all file paths with the specified value.
await Bun.build({
entrypoints: ['./index.tsx'],
outdir: './out',
publicPath: 'https://cdn.example.com/', // default is undefined
})
bun build ./index.tsx --outdir ./out --public-path https://cdn.example.com/
The output file would now look something like this.
var logo = './logo-a7305bdef.svg';
var logo = 'https://cdn.example.com/logo-a7305bdef.svg';
define
A map of global identifiers to be replaced at build time. Keys of this object are identifier names, and values are JSON strings that will be inlined.
await Bun.build({
entrypoints: ['./index.tsx'],
outdir: './out',
define: {
STRING: JSON.stringify("value"),
"nested.boolean": "true",
},
})
bun build ./index.tsx --outdir ./out --define 'STRING="value"' --define "nested.boolean=true"
loader
A map of file extensions to built-in loader names. This can be used to quickly customize how certain files are loaded.
await Bun.build({
entrypoints: ['./index.tsx'],
outdir: './out',
loader: {
".png": "dataurl",
".txt": "file",
},
})
bun build ./index.tsx --outdir ./out --loader .png:dataurl --loader .txt:file
banner
A banner to be added to the final bundle, this can be a directive like "use client" for react or a comment block such as a license for the code.
await Bun.build({
entrypoints: ['./index.tsx'],
outdir: './out',
banner: '"use client";'
})
bun build ./index.tsx --outdir ./out --banner "\"use client\";"
footer
A footer to be added to the final bundle, this can be something like a comment block for a license or just a fun easter egg.
await Bun.build({
entrypoints: ['./index.tsx'],
outdir: './out',
footer: '// built with love in SF'
})
bun build ./index.tsx --outdir ./out --footer="// built with love in SF"
drop
Remove function calls from a bundle. For example, --drop=console
will remove all calls to console.log
. Arguments to calls will also be removed, regardless of if those arguments may have side effects. Dropping debugger
will remove all debugger
statements.
await Bun.build({
entrypoints: ['./index.tsx'],
outdir: './out',
drop: ["console", "debugger", "anyIdentifier.or.propertyAccess"],
})
bun build ./index.tsx --outdir ./out --drop=console --drop=debugger --drop=anyIdentifier.or.propertyAccess
experimentalCss
Whether to enable experimental support for bundling CSS files. Defaults to false
. In 1.2, this property will be deleted, and CSS bundling will always be enabled.
This supports bundling CSS files imported from JS, as well as CSS entrypoints.
const result = await Bun.build({
entrypoints: ["./index.ts"],
experimentalCss: true,
});
// => { success: boolean, outputs: BuildArtifact[], logs: BuildMessage[] }
throw
If set to true
, Bun.build
will throw on build failure. See the section "Logs and Errors" for more details on the error message structure.
In 1.2, this will default to true
, with the previous behavior as throw: false
Outputs
The Bun.build
function returns a Promise<BuildOutput>
, defined as:
interface BuildOutput {
outputs: BuildArtifact[];
success: boolean;
logs: Array<object>; // see docs for details
}
interface BuildArtifact extends Blob {
kind: "entry-point" | "chunk" | "asset" | "sourcemap";
path: string;
loader: Loader;
hash: string | null;
sourcemap: BuildArtifact | null;
}
The outputs
array contains all the files that were generated by the build. Each artifact implements the Blob
interface.
const build = await Bun.build({
/* */
});
for (const output of build.outputs) {
await output.arrayBuffer(); // => ArrayBuffer
await output.bytes(); // => Uint8Array
await output.text(); // string
}
Each artifact also contains the following properties:
kind | What kind of build output this file is. A build generates bundled entrypoints, code-split "chunks", sourcemaps, bytecode, and copied assets (like images). |
path | Absolute path to the file on disk |
loader | The loader was used to interpret the file. See Bundler > Loaders to see how Bun maps file extensions to the appropriate built-in loader. |
hash | The hash of the file contents. Always defined for assets. |
sourcemap | The sourcemap file corresponding to this file, if generated. Only defined for entrypoints and chunks. |
Similar to BunFile
, BuildArtifact
objects can be passed directly into new Response()
.
const build = await Bun.build({
/* */
});
const artifact = build.outputs[0];
// Content-Type header is automatically set
return new Response(artifact);
The Bun runtime implements special pretty-printing of BuildArtifact
object to make debugging easier.
// build.ts
const build = await Bun.build({/* */});
const artifact = build.outputs[0];
console.log(artifact);
bun run build.ts
BuildArtifact (entry-point) {
path: "./index.js",
loader: "tsx",
kind: "entry-point",
hash: "824a039620219640",
Blob (114 bytes) {
type: "text/javascript;charset=utf-8"
},
sourcemap: null
}
Bytecode
The bytecode: boolean
option can be used to generate bytecode for any JavaScript/TypeScript entrypoints. This can greatly improve startup times for large applications. Only supported for "cjs"
format, only supports "target": "bun"
and dependent on a matching version of Bun. This adds a corresponding .jsc
file for each entrypoint.
await Bun.build({
entrypoints: ["./index.tsx"],
outdir: "./out",
bytecode: true,
})
bun build ./index.tsx --outdir ./out --bytecode
Executables
Bun supports "compiling" a JavaScript/TypeScript entrypoint into a standalone executable. This executable contains a copy of the Bun binary.
bun build ./cli.tsx --outfile mycli --compile
./mycli
Refer to Bundler > Executables for complete documentation.
Logs and errors
By default, Bun.build
only throws if invalid options are provided. Read the success
property to determine if the build was successful; the logs
property will contain additional details.
const result = await Bun.build({
entrypoints: ["./index.tsx"],
outdir: "./out",
});
if (!result.success) {
console.error("Build failed");
for (const message of result.logs) {
// Bun will pretty print the message object
console.error(message);
}
}
Each message is either a BuildMessage
or ResolveMessage
object, which can be used to trace what problems happened in the build.
class BuildMessage {
name: string;
position?: Position;
message: string;
level: "error" | "warning" | "info" | "debug" | "verbose";
}
class ResolveMessage extends BuildMessage {
code: string;
referrer: string;
specifier: string;
importKind: ImportKind;
}
If you want to throw an error from a failed build, consider passing the logs to an AggregateError
. If uncaught, Bun will pretty-print the contained messages nicely.
if (!result.success) {
throw new AggregateError(result.logs, "Build failed");
}
In Bun 1.2, throwing an aggregate error like this will become the default beahavior. You can opt-into it early using the throw: true
option.
try {
const result = await Bun.build({
entrypoints: ["./index.tsx"],
outdir: "./out",
});
} catch (e) {
// TypeScript does not allow annotations on the catch clause
const error = e as AggregateError;
console.error("Build Failed");
// Example: Using the built-in formatter
console.error(error);
// Example: Serializing the failure as a JSON string.
console.error(JSON.stringify(error, null, 2));
}
Reference
interface Bun {
build(options: BuildOptions): Promise<BuildOutput>;
}
interface BuildConfig {
entrypoints: string[]; // list of file path
outdir?: string; // output directory
target?: Target; // default: "browser"
/**
* Output module format. Top-level await is only supported for `"esm"`.
*
* Can be:
* - `"esm"`
* - `"cjs"` (**experimental**)
* - `"iife"` (**experimental**)
*
* @default "esm"
*/
format?: "esm" | "cjs" | "iife";
naming?:
| string
| {
chunk?: string;
entry?: string;
asset?: string;
};
root?: string; // project root
splitting?: boolean; // default true, enable code splitting
plugins?: BunPlugin[];
external?: string[];
packages?: "bundle" | "external";
publicPath?: string;
define?: Record<string, string>;
loader?: { [k in string]: Loader };
sourcemap?: "none" | "linked" | "inline" | "external" | "linked" | boolean; // default: "none", true -> "inline"
/**
* package.json `exports` conditions used when resolving imports
*
* Equivalent to `--conditions` in `bun build` or `bun run`.
*
* https://nodejs.org/api/packages.html#exports
*/
conditions?: Array<string> | string;
/**
* Controls how environment variables are handled during bundling.
*
* Can be one of:
* - `"inline"`: Injects environment variables into the bundled output by converting `process.env.FOO`
* references to string literals containing the actual environment variable values
* - `"disable"`: Disables environment variable injection entirely
* - A string ending in `*`: Inlines environment variables that match the given prefix.
* For example, `"MY_PUBLIC_*"` will only include env vars starting with "MY_PUBLIC_"
*/
env?: "inline" | "disable" | `${string}*`;
minify?:
| boolean
| {
whitespace?: boolean;
syntax?: boolean;
identifiers?: boolean;
};
/**
* Ignore dead code elimination/tree-shaking annotations such as @__PURE__ and package.json
* "sideEffects" fields. This should only be used as a temporary workaround for incorrect
* annotations in libraries.
*/
ignoreDCEAnnotations?: boolean;
/**
* Force emitting @__PURE__ annotations even if minify.whitespace is true.
*/
emitDCEAnnotations?: boolean;
/**
* Generate bytecode for the output. This can dramatically improve cold
* start times, but will make the final output larger and slightly increase
* memory usage.
*
* Bytecode is currently only supported for CommonJS (`format: "cjs"`).
*
* Must be `target: "bun"`
* @default false
*/
bytecode?: boolean;
/**
* Add a banner to the bundled code such as "use client";
*/
banner?: string;
/**
* Add a footer to the bundled code such as a comment block like
*
* `// made with bun!`
*/
footer?: string;
/**
* **Experimental**
*
* Enable CSS support.
*/
experimentalCss?: boolean;
/**
* Drop function calls to matching property accesses.
*/
drop?: string[];
/**
* When set to `true`, the returned promise rejects with an AggregateError when a build failure happens.
* When set to `false`, the `success` property of the returned object will be `false` when a build failure happens.
*
* This defaults to `false` in Bun 1.1 and will change to `true` in Bun 1.2
* as most usage of `Bun.build` forgets to check for errors.
*/
throw?: boolean;
}
interface BuildOutput {
outputs: BuildArtifact[];
success: boolean;
logs: Array<BuildMessage | ResolveMessage>;
}
interface BuildArtifact extends Blob {
path: string;
loader: Loader;
hash: string | null;
kind: "entry-point" | "chunk" | "asset" | "sourcemap" | "bytecode";
sourcemap: BuildArtifact | null;
}
type Loader =
| "js"
| "jsx"
| "ts"
| "tsx"
| "json"
| "toml"
| "file"
| "napi"
| "wasm"
| "text";
interface BuildOutput {
outputs: BuildArtifact[];
success: boolean;
logs: Array<BuildMessage | ResolveMessage>;
}
declare class ResolveMessage {
readonly name: "ResolveMessage";
readonly position: Position | null;
readonly code: string;
readonly message: string;
readonly referrer: string;
readonly specifier: string;
readonly importKind:
| "entry_point"
| "stmt"
| "require"
| "import"
| "dynamic"
| "require_resolve"
| "at"
| "at_conditional"
| "url"
| "internal";
readonly level: "error" | "warning" | "info" | "debug" | "verbose";
toString(): string;
}