esw

0.15.0 verified Fri May 01 auth: no javascript

esw is a zero-configuration JavaScript/TypeScript library build tool that leverages esbuild for blazing fast performance. Version 0.15.0 is the current stable release, with a moderate release cadence. It infers build options from package.json fields (main, module, type) and automatically excludes dependencies and peerDependencies from the bundle. Unlike tsdx or tsup, esw focuses on minimal configuration and esbuild CLI compatibility. Supports Node.js >=14.14.0 and outputs both CommonJS and ESM formats.

Common errors

error Error: Could not resolve entry point ↓

cause No source files found at default location (src/index.ts) or specified path is incorrect.

fix

Create src/index.ts or specify entry point explicitly: esw build src/main.ts

error esw: command not found ↓

cause esw is not installed or not in PATH.

fix

Run 'npm install esw --save-dev' and use 'npx esw' or add to scripts in package.json.

error TypeError: Cannot read properties of undefined (reading 'main') ↓

cause package.json is missing or does not have 'main' field when esw tries to infer output.

fix

Ensure package.json exists and contains a 'main' field.

Warnings

gotcha esw relies on package.json fields. If main/module are not declared, build may produce no output or fail silently. ↓

fix Ensure package.json has 'main' and/or 'module' fields pointing to desired output paths.

gotcha The output format for the 'module' field is always treated as ESM; do not expect CJS for that field. ↓

fix Use 'main' for CommonJS output, 'module' for ESM output.

gotcha esw uses esbuild internally; some esbuild options may not be fully supported or behave differently. ↓

fix Refer to esbuild documentation for option compatibility.

Install

npm install esw

yarn add esw

pnpm add esw

Imports

esw
wrong
```
const esw = require('esw')
```
correct
```
import esw from 'esw'
```
esw is a CLI tool; programmatic API is not exposed. The import shown is a placeholder; actual usage is via CLI commands like `npx esw build`.

Quickstart

Create a TypeScript library, configure package.json, and run esw build to output both CJS and ESM bundles in dist/ folder.

mkdir my-lib && cd my-lib
npm init -y
npm i esw -D
# Edit package.json to add main/module fields
echo '{"name":"my-lib","main":"dist/index.cjs.js","module":"dist/index.esm.js","scripts":{"build":"esw build"}}' > package.json
mkdir src
echo 'export const add = (a,b) => a+b' > src/index.ts
npm run build
ls dist