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.
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.
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.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 'warning' event.
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.
System calls like open(2) and read(2) define the interface between user programs
and the underlying operating system. Node.js 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.