Output Format

By default, tsdown generates JavaScript code in the ESM (ECMAScript Module) format. However, you can specify the desired output format using the --format option:

tsdown --format esm # default

Available Formats

• esm: ECMAScript Module format, ideal for modern JavaScript environments, including browsers and Node.js.
• cjs: CommonJS format, commonly used in Node.js projects.
• iife: Immediately Invoked Function Expression, suitable for embedding in <script> tags or standalone browser usage.

Example

# Generate ESM output (default)
tsdown --format esm

# Generate both ESM and CJS outputs
tsdown --format esm --format cjs

# Generate IIFE output for browser usage
tsdown --format iife

TIP

You can specify multiple formats in a single command to generate outputs for different environments. For example, combining esm and cjs ensures compatibility with both modern and legacy systems.