Bun

Fast all-in-one JavaScript runtime, bundler, test runner, and package manager.

Quick Start

bun init              # Create new project
bun install           # Install dependencies
bun run ./file.ts     # Run a script
bun test              # Run tests

Package Management

# Installation
bun add <pkg>              # Production dep
bun add -d <pkg>           # Dev dependency
bun add --optional <pkg>   # Optional dep
bun add -g <pkg>           # Global install
bun add <pkg>@^1.0.0       # Specific version
bun add <owner>/<repo>     # From git

# Management
bun remove <pkg>           # Remove package
bun update                 # Update all
bun update <pkg>           # Update specific
bun outdated               # Show outdated
bun audit                  # Security audit
bun why <pkg>              # Why installed
bun info <pkg>             # Package metadata
bun publish                # Publish to npm
bun patch <pkg>            # Patch a package
bun link                   # Link local package
bun unlink                 # Unlink local package

Running Code

bun run ./file.ts          # Execute file
bun run dev                # Run script from package.json
bun -e "code"              # Eval code
bun exec ./script.sh       # Run shell script
bun run ./cli.ts arg1 arg2 # With arguments

# Long-running/watch mode (use tmux)
tmux new -d -s dev 'bun run --watch ./file.ts'
tmux new -d -s hot 'bun run --hot ./file.ts'
tmux new -d -s repl 'bun repl'

Testing

bun test                   # Run all tests
bun test tests/test.ts     # Specific file
bun test --coverage        # With coverage
bun test -t "pattern"      # Filter by name
bun test --bail 3          # Stop after N failures
bun test -u                # Update snapshots
bun test --timeout 5000    # With timeout
bun test --verbose         # Verbose output

# Watch mode (use tmux)
tmux new -d -s test 'bun test --watch'

Building

bun build ./src/index.ts              # Bundle
bun build --production ./src/index.ts # Minified
bun build --target=node ./src/index.ts # Node target
bun build --compile ./cli.ts          # Standalone executable
bun build --splitting ./src/index.ts  # Code splitting
bun build --outdir ./dist ./src/index.ts # Output directory

Configuration

bunfig.toml

[install]
linker = "hoisted"
minimumReleaseAge = 259200

[test]
timeout = 5000
coverage = { reporter = ["text"] }

[build]
minify = true
sourcemap = "external"
outdir = "dist"

package.json

{
  "name": "my-project",
  "type": "module",
  "module": "src/index.ts",
  "scripts": {
    "dev": "bun run --watch src/index.ts",
    "test": "bun test"
  }
}

Workspaces

{
  "workspaces": ["packages/*"],
  "catalog": {
    "react": "^18.0.0",
    "typescript": "^5.0.0"
  }
}

bun run --workspaces test    # Run in all workspaces
bun add <pkg> --filter <ws>  # Add to specific workspace

Environment Variables

bun run --env-file=.env dev  # Load .env
VAR=value bun run ./file.ts  # Set inline
process.env.VAR              # Access in code

Tips

• Use bunx for one-off CLIs (auto-installs)
• Commit bun.lock for reproducible installs
• Use --frozen-lockfile in CI
• Use bun run -i to auto-install missing deps
• Standalone executables: bun build --compile
• Use tmux for watch/hot modes