# esbuild-plugins-node-modules-polyfill
**Polyfills nodejs builtin modules for the browser.**
[](https://github.com/imranbarbhuiya/esbuild-plugins-node-modules-polyfill/blob/main/LICENSE)
[](https://www.npmjs.com/package/esbuild-plugins-node-modules-polyfill)
## Description
Polyfills nodejs builtin modules and globals for the browser.
## Features
- Written In Typescript
- Offers CJS and ESM builds
- Full TypeScript & JavaScript support
- Supports `node:` protocol
- Supports [`browser` field in `package.json`](https://github.com/defunctzombie/package-browser-field-spec)
- Optionally injects globals
- Optionally provides empty fallbacks
- Supports custom polyfill overrides
## Install
```bash
npm install --save-dev esbuild-plugins-node-modules-polyfill
```
## Usage
```ts
import { nodeModulesPolyfillPlugin } from 'esbuild-plugins-node-modules-polyfill';
import { build } from 'esbuild';
build({
plugins: [nodeModulesPolyfillPlugin()],
});
```
### Inject globals when detected:
```ts
import { nodeModulesPolyfillPlugin } from 'esbuild-plugins-node-modules-polyfill';
import { build } from 'esbuild';
build({
plugins: [
nodeModulesPolyfillPlugin({
globals: {
process: true,
Buffer: true,
},
}),
],
});
```
> [!Note]
> If you are utilizing the [`modules`](#configure-which-modules-to-polyfill) option, ensure that you include polyfills for the global modules you are using.
### Configure which modules to polyfill:
```ts
import { nodeModulesPolyfillPlugin } from 'esbuild-plugins-node-modules-polyfill';
import { build } from 'esbuild';
build({
plugins: [
nodeModulesPolyfillPlugin({
modules: ['crypto'],
}),
],
});
```
```ts
import { nodeModulesPolyfillPlugin } from 'esbuild-plugins-node-modules-polyfill';
import { build } from 'esbuild';
build({
plugins: [
nodeModulesPolyfillPlugin({
modules: {
crypto: true,
fs: false,
},
}),
],
});
```
### Override polyfills with custom implementations:
You can provide custom polyfill implementations for specific modules. This is useful when you need to customize the behavior of a polyfill for your specific use case.
```ts
import { nodeModulesPolyfillPlugin } from 'esbuild-plugins-node-modules-polyfill';
import { build } from 'esbuild';
build({
plugins: [
nodeModulesPolyfillPlugin({
overrides: {
process: './my-custom-process-polyfill.js',
},
}),
],
});
```
The custom polyfill file should export a default export with your implementation:
```js
// my-custom-process-polyfill.js
const customProcess = {
env: {},
version: 'v1.0.0',
platform: 'browser',
stdout: {
write: (data) => console.log(data),
},
// ... other process properties
};
export default customProcess;
```
> [!Note]
> Custom overrides work with both `process` and `node:process` style imports. You can specify the override with or without the `node:` prefix.
> [!Important]
> - File paths should be **absolute paths** or **relative to the project root** (where esbuild is executed), not relative to the configuration file. This is important because esbuild will resolve these paths, and relative paths might not work as expected if you run the build command from a different directory.
> - If a module is specified in both `overrides` and `modules` options (e.g., `overrides: { process: './custom.js' }` and `modules: { process: 'empty' }`), the **override takes precedence** and the `modules` configuration for that module will be ignored.
### Provide empty polyfills:
#### Provide empty polyfills for specific modules:
```ts
import { nodeModulesPolyfillPlugin } from 'esbuild-plugins-node-modules-polyfill';
import { build } from 'esbuild';
build({
plugins: [
nodeModulesPolyfillPlugin({
modules: {
fs: 'empty',
crypto: true,
},
}),
],
});
```
#### Provide empty fallbacks for any unpolyfilled modules:
```ts
import { nodeModulesPolyfillPlugin } from 'esbuild-plugins-node-modules-polyfill';
import { build } from 'esbuild';
build({
plugins: [
nodeModulesPolyfillPlugin({
fallback: 'empty',
}),
],
});
```
#### Provide empty fallbacks for any unconfigured modules:
```ts
import { nodeModulesPolyfillPlugin } from 'esbuild-plugins-node-modules-polyfill';
import { build } from 'esbuild';
build({
plugins: [
nodeModulesPolyfillPlugin({
fallback: 'empty',
modules: {
crypto: true,
},
}),
],
});
```
### Fail the build when certain modules are used:
> [!Important]
> The `write` option in `esbuild` must be `false` to support this.
```ts
import { nodeModulesPolyfillPlugin } from 'esbuild-plugins-node-modules-polyfill';
import { build } from 'esbuild';
const buildResult = await build({
write: false,
plugins: [
nodeModulesPolyfillPlugin({
modules: {
crypto: 'error',
path: true,
},
}),
],
});
```
### Fail the build when a module is not polyfilled or configured:
> [!Important]
> The `write` option in `esbuild` must be `false` to support this.
```ts
import { nodeModulesPolyfillPlugin } from 'esbuild-plugins-node-modules-polyfill';
import { build } from 'esbuild';
const buildResult = await build({
write: false,
plugins: [
nodeModulesPolyfillPlugin({
fallback: 'error',
modules: {
path: true,
},
}),
],
});
```
### Provide a custom error formatter when a module is not polyfilled or configured:
Return an esbuild `PartialMessage` object from the `formatError` function to override any properties of the default error message.
> [!Important]
> The `write` option in `esbuild` must be `false` to support this.
```ts
import { nodeModulesPolyfillPlugin } from 'esbuild-plugins-node-modules-polyfill';
import { build } from 'esbuild';
const buildResult = await build({
write: false,
plugins: [
nodeModulesPolyfillPlugin({
fallback: 'error',
modules: {
path: true,
},
formatError({ moduleName, importer, polyfillExists }) {
return {
text: polyfillExists
? `Polyfill has not been configured for "${moduleName}", imported by "${importer}"`
: `Polyfill does not exist for "${moduleName}", imported by "${importer}"`,
};
},
}),
],
});
```
## Buy me some doughnuts
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## Contributors ✨
Thanks goes to these wonderful people:
