Node.js

- About these Docs
- Usage & Example

- Assertion Testing
- Async Hooks
- Buffer
- C++ Addons
- C/C++ Addons - N-API
- Child Processes
- Cluster
- Command Line Options
- Console
- Crypto
- Debugger
- Deprecated APIs
- DNS
- Domain
- ECMAScript Modules
- Errors
- Events
- File System
- Globals
- HTTP
- HTTP/2
- HTTPS
- Inspector
- Internationalization
- Modules
- Net
- OS
- Path
- Performance Hooks
- Process
- Punycode
- Query Strings
- Readline
- REPL
- Stream
- String Decoder
- Timers
- TLS/SSL
- Tracing
- TTY
- UDP/Datagram
- URL
- Utilities
- V8
- VM
- ZLIB

- GitHub Repo & Issue Tracker
- Mailing List

# About this Documentation#

The goal of this documentation is to comprehensively explain the Node.js API, both from a reference as well as a conceptual point of view. Each section describes a built-in module or high-level concept.

Where appropriate, property types, method arguments, and the arguments provided to event handlers are detailed in a list underneath the topic heading.

## Contributing#

If errors are found in this documentation, please submit an issue or see the contributing guide for directions on how to submit a patch.

Every file is generated based on the corresponding `.md` file in the `doc/api/` folder in Node.js's source tree. The documentation is generated using the `tools/doc/generate.js` program. An HTML template is located at `doc/template.html`.

## Stability Index#

Throughout the documentation are indications of a section's stability. The Node.js API is still somewhat changing, and as it matures, certain parts are more reliable than others. Some are so proven, and so relied upon, that they are unlikely to ever change at all. Others are brand new and experimental, or known to be hazardous and in the process of being redesigned.

The stability indices are as follows:

Stability: 0 - Deprecated This feature is known to be problematic, and changes may be planned. Do not rely on it. Use of the feature may cause warnings to be emitted. Backwards compatibility across major versions should not be expected.
Stability: 1 - Experimental This feature is still under active development and subject to non-backwards compatible changes, or even removal, in any future version. Use of the feature is not recommended in production environments. Experimental features are not subject to the Node.js Semantic Versioning model.
Stability: 2 - Stable The API has proven satisfactory. Compatibility with the npm ecosystem is a high priority, and will not be broken unless absolutely necessary.

Note: Caution must be used when making use of `Experimental` features, particularly within modules that may be used as dependencies (or dependencies of dependencies) within a Node.js application. End users may not be aware that experimental features are being used, and therefore may experience unexpected failures or behavior changes when API modifications occur. To help avoid such surprises, `Experimental` features may require a command-line flag to explicitly enable them, or may cause a process warning to be emitted. By default, such warnings are printed to `stderr` and may be handled by attaching a listener to the `process.on('warning')` event.

## JSON Output#

Added in: v0.6.12
Stability: 1 - Experimental

Every `.html` document has a corresponding `.json` document presenting the same information in a structured manner. This feature is experimental, and added for the benefit of IDEs and other utilities that wish to do programmatic things with the documentation.

## Syscalls and man pages#

System calls like open(2) and read(2) define the interface between user programs and the underlying operating system. Node functions which simply wrap a syscall, like `fs.open()`, will document that. The docs link to the corresponding man pages (short for manual pages) which describe how the syscalls work.

Some syscalls, like lchown(2), are BSD-specific. That means, for example, that `fs.lchown()` only works on macOS and other BSD-derived systems, and is not available on Linux.

Most Unix syscalls have Windows equivalents, but behavior may differ on Windows relative to Linux and macOS. For an example of the subtle ways in which it's sometimes impossible to replace Unix syscall semantics on Windows, see Node issue 4760.