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tessl/npm-parcel

Zero configuration web application bundler with blazing fast performance and comprehensive dev server

Workspace
tessl
Visibility
Public
Created
Last updated
Describes
npmpkg:npm/parcel@2.15.x

To install, run

npx @tessl/cli install tessl/npm-parcel@2.15.0
0
# Parcel
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Parcel is a blazing fast, zero configuration web application bundler designed for modern web development. Built with performance in mind, it features a JavaScript compiler written in Rust for native performance, parallel processing using worker threads, and comprehensive caching to avoid rebuilding unchanged code.
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## Package Information
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- **Package Name**: parcel
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- **Package Type**: npm
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- **Language**: JavaScript/TypeScript
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- **Installation**: `npm install -g parcel` or `npm install --save-dev parcel`
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## Core Usage
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Parcel is a CLI-only tool that provides zero-configuration bundling through command-line interface:
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```bash
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# Start development server (default command)
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parcel index.html
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# Build for production
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parcel build index.html
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# Watch mode without dev server
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parcel watch index.html
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# Get help
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parcel help
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```
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## Basic Usage
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```bash
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# Install Parcel globally
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npm install -g parcel
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# Create a simple HTML file
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echo '<html><body><script src="./app.js"></script></body></html>' > index.html
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echo 'console.log("Hello Parcel!");' > app.js
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# Start development server
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parcel index.html
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# ✨ Built in 123ms
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# Server running at http://localhost:1234
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# Build for production
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parcel build index.html
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# ✨ Built in 456ms
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# dist/index.html      1.23 KB    123ms
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# dist/app.js          2.45 KB      0ms
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```
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## Architecture
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Parcel operates as a command-line tool that orchestrates the build process through several key components:
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- **CLI Interface**: Command-line commands (`serve`, `watch`, `build`, `help`) that accept various options
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- **Development Server**: Built-in dev server with hot module replacement for development workflow
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- **Build Pipeline**: Production build system with optimizations like minification and tree-shaking
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- **File System Watcher**: Monitors file changes for automatic rebuilds in development
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- **Configuration System**: Zero-config approach with optional configuration files
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## Capabilities
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### Development Server
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Start a development server with hot module replacement for rapid development workflow.
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```bash { .api }
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parcel serve [input...]
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# or simply:
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parcel [input...]
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# Common options:
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# --port <port>          Set server port (default: 1234)
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# --host <host>          Set host to listen on
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# --https                Serve files over HTTPS
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# --cert <path>          Path to HTTPS certificate
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# --key <path>           Path to HTTPS private key
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# --open [browser]       Auto-open in browser
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# --public-url <url>     Path prefix for absolute URLs
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# --lazy [includes]      Build async bundles on demand, when requested in the browser
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# --lazy-exclude <excludes>  Can only be used with --lazy. Exclude from lazy building
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# --watch-for-stdin      Exit when stdin closes
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```
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**Usage Examples:**
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```bash
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# Basic development server
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parcel index.html
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# Custom port and host
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parcel serve src/index.html --port 3000 --host 0.0.0.0
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# HTTPS development server
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parcel index.html --https --cert ./cert.pem --key ./key.pem
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# Auto-open in default browser
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parcel index.html --open
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# Lazy loading for large applications
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parcel index.html --lazy "src/pages/**/*.js"
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# Lazy loading with exclusions
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parcel index.html --lazy --lazy-exclude "src/critical/**/*.js"
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```
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### Production Build
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Bundle application for production with optimizations enabled.
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```bash { .api }
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parcel build [input...]
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# Common options:
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# --no-optimize         Disable minification
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# --no-scope-hoist      Disable scope-hoisting  
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# --public-url <url>    Path prefix for absolute URLs
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# --no-content-hash     Disable content hashing
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# --dist-dir <dir>      Output directory
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# --target [name]       Build specific targets
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```
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**Usage Examples:**
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```bash
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# Basic production build
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parcel build index.html
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# Custom output directory
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parcel build src/index.html --dist-dir build
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# Disable optimizations for debugging
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parcel build index.html --no-optimize --no-scope-hoist
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# Build for specific targets
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parcel build index.html --target web --target node
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# Custom public URL for CDN deployment
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parcel build index.html --public-url https://cdn.example.com/
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```
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### Watch Mode
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Monitor files for changes and rebuild automatically without development server.
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```bash { .api }
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parcel watch [input...]
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# Common options:
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# --public-url <url>    Path prefix for absolute URLs
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# --no-content-hash     Disable content hashing
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# --watch-for-stdin     Exit when stdin closes
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# HMR options (same as serve command):
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# --no-hmr              Disable hot module replacement
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# --hmr-port <port>     Hot module replacement port
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# --hmr-host <host>     Hot module replacement host
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```
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**Usage Examples:**
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```bash
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# Basic watch mode
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parcel watch index.html
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# Watch with custom settings
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parcel watch src/index.html --no-content-hash --public-url /assets/
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```
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### Help System
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Get help information for commands and options.
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```bash { .api }
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parcel help [command]
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# Examples:
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parcel help           # General help
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parcel help serve     # Help for serve command
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parcel help build     # Help for build command
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```
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## Global Options
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These options are available across all commands:
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### Cache & Performance
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```bash { .api }
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# Cache control
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--no-cache              # Disable filesystem cache
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--cache-dir <path>      # Set cache directory (default: .parcel-cache)
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# Performance monitoring
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--profile               # Enable sampling build profiling
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--trace                 # Enable build tracing
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--detailed-report [count]  # Print asset timings and sizes
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```
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### File Watching
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```bash { .api }
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# Watch configuration
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--watch-dir <path>      # Set root watch directory (defaults to nearest lockfile or source control dir)
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--watch-ignore [paths]  # Directories to ignore (comma-separated, defaults to '.git,.hg')
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--watch-backend <name>  # Set watcher backend
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                       # Choices: brute-force, watchman, fs-events, inotify, windows
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```
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### Build Configuration
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```bash { .api }
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# Configuration
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--config <path>         # Specify config path or package name
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--no-source-maps        # Disable sourcemaps
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--target [name]         # Build specific targets (can be used multiple times)
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--no-autoinstall        # Disable automatic dependency installation
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```
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### Hot Module Replacement
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```bash { .api }
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# HMR configuration (serve/watch commands)
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--no-hmr               # Disable hot module replacement
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--hmr-port <port>      # Hot module replacement port
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--hmr-host <host>      # Hot module replacement host
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```
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### Logging & Reporting
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```bash { .api }
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# Logging
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--log-level <level>    # Set log level
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                      # Choices: none, error, warn, info, verbose
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# Reporting
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--reporter <name>      # Additional reporters (can be used multiple times)
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```
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### Feature Flags
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```bash { .api }
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# Feature flags
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--feature-flag <name=value>  # Set feature flag values
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                            # Format: --feature-flag name=true
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                            # Available flags: exampleFeature, useWatchmanWatcher
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```
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### Version Information
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```bash { .api }
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# Version
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-V, --version          # Output version number
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```
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## Entry Point Discovery
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Parcel automatically discovers entry points based on file extensions and content:
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- **HTML files**: `index.html`, `src/index.html`
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- **JavaScript/TypeScript**: `index.js`, `main.js`, `app.js`, `src/index.ts`
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- **Package.json**: Uses `main`, `module`, or `browser` fields
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- **Multiple entries**: `parcel build src/*.html` for multiple pages
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## Target Environments
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Parcel supports multiple build targets:
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- **Web browsers**: Modern ES modules and legacy compatibility
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- **Node.js**: Server-side applications and utilities
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- **Electron**: Desktop applications
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- **Web Workers**: Background processing scripts
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## Configuration Files
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While zero-config by default, Parcel supports optional configuration:
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- `.parcelrc`: Main configuration file
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- `package.json`: Browserslist, source fields
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- `tsconfig.json`: TypeScript configuration
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- `postcss.config.js`: PostCSS configuration
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## Error Handling
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Parcel provides detailed error messages and diagnostics:
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- **Build errors**: Syntax errors, missing dependencies, type errors
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- **Runtime errors**: Hot reload error overlay in development
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- **Performance warnings**: Bundle size, unused dependencies
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- **Detailed stack traces**: Source map support for debugging
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## Runtime Controls
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While Parcel is running, these keyboard shortcuts are available:
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```bash { .api }
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# Keyboard shortcuts during runtime
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Ctrl+C    # Graceful exit
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Ctrl+E    # Toggle profiling
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Ctrl+Y    # Take heap snapshot
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```
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## Environment Variables
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Parcel recognizes several environment variables:
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- `NODE_ENV`: Automatically set based on command (`development` for serve/watch, `production` for build)
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- `PORT`: Default port for development server (defaults to 1234)
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- `HMR_PORT`: Default HMR port
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- `HMR_HOST`: Default HMR host
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- `CI`: When detected, disables autoinstall for build command
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- `PARCEL_BUILD_ENV`: Internal build environment control
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## Port Behavior
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Parcel handles ports intelligently:
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- **Default port**: 1234 or value from `$PORT` environment variable
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- **Port occupied**: Automatically finds next available port
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- **User-specified port**: Fails if port is not available (no auto-discovery)
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- **HMR port**: Separate port for hot module replacement (from `$HMR_PORT`)
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## Mode Detection
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Parcel automatically sets the build mode:
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- **Production mode**: `parcel build` command (enables optimizations)
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- **Development mode**: `parcel serve` and `parcel watch` commands (enables debugging features)