99 lines
1.9 KiB
Markdown
99 lines
1.9 KiB
Markdown
# CJS Default Export
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Control how default exports are handled in CommonJS output.
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## Overview
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The `cjsDefault` option improves compatibility when generating CommonJS modules. When enabled (default), modules with only a single default export use `module.exports = ...` instead of `exports.default = ...`.
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## Type
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```ts
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cjsDefault?: boolean // default: true
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```
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## Basic Usage
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### Enabled (Default)
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```ts
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export default defineConfig({
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entry: ['src/index.ts'],
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format: ['cjs'],
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cjsDefault: true, // default behavior
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})
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```
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### Disabled
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```ts
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export default defineConfig({
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entry: ['src/index.ts'],
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format: ['cjs'],
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cjsDefault: false,
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})
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```
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## How It Works
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### With `cjsDefault: true` (Default)
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When your module has **only a single default export**, tsdown transforms:
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**Source:**
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```ts
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// src/index.ts
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export default function greet() {
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console.log('Hello, world!')
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}
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```
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**Generated CJS:**
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```js
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// dist/index.cjs
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function greet() {
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console.log('Hello, world!')
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}
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module.exports = greet
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```
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**Generated Declaration:**
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```ts
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// dist/index.d.cts
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declare function greet(): void
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export = greet
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```
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This allows consumers to use `const greet = require('your-module')` directly.
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### With `cjsDefault: false`
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The default export stays as `exports.default`:
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```js
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// dist/index.cjs
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function greet() {
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console.log('Hello, world!')
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}
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exports.default = greet
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```
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Consumers need `require('your-module').default`.
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## When to Disable
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- When your module has both default and named exports
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- When you need consistent `exports.default` behavior
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- When consumers always use ESM imports
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## Tips
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1. **Leave enabled** for most libraries (default `true`)
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2. **Disable** if you have both default and named exports and need consistent behavior
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3. **Test CJS consumers** to verify compatibility
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## Related Options
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- [Output Format](option-output-format.md) - Module formats
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- [Shims](option-shims.md) - ESM/CJS compatibility
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