Usage in Deno
import * as mod from "node:util";
The node:util module supports the needs of Node.js internal APIs. Many of the
utilities are useful for application and module developers as well. To access
it:
const util = require('node:util');
The MIMEParams API provides read and write access to the parameters of aMIMEType.
An implementation of the MIMEType class.
An implementation of the WHATWG Encoding Standard TextDecoder API.
An implementation of the WHATWG Encoding Standard TextEncoder API. All
instances of TextEncoder only support UTF-8 encoding.
Listens to abort event on the provided signal and
returns a promise that is fulfilled when the signal is
aborted. If the passed resource is garbage collected before the signal is
aborted, the returned promise shall remain pending indefinitely.
Takes an async function (or a function that returns a Promise) and returns a
function following the error-first callback style, i.e. taking
an (err, value) => ... callback as the last argument. In the callback, the
first argument will be the rejection reason (or null if the Promiseresolved), and the second argument will be the resolved value.
The util.debuglog() method is used to create a function that conditionally
writes debug messages to stderr based on the existence of the NODE_DEBUGenvironment variable. If the section name appears within the value of that
environment variable, then the returned function operates similar to console.error(). If not, then the returned function is a no-op.
The util.deprecate() method wraps fn (which may be a function or class) in
such a way that it is marked as deprecated.
The util.format() method returns a formatted string using the first argument
as a printf-like format string which can contain zero or more format
specifiers. Each specifier is replaced with the converted value from the
corresponding argument. Supported specifiers are:
Returns a Map of all system error codes available from the Node.js API.
The mapping between error codes and error names is platform-dependent.
See Common System Errors for the names of common errors.
Returns the string name for a numeric error code that comes from a Node.js API.
The mapping between error codes and error names is platform-dependent.
See Common System Errors for the names of common errors.
Usage of util.inherits() is discouraged. Please use the ES6 class andextends keywords to get language level inheritance support. Also note
that the two styles are semantically incompatible.
The util.inspect() method returns a string representation of object that is
intended for debugging. The output of util.inspect may change at any time
and should not be depended upon programmatically. Additional options may be
passed that alter the result.util.inspect() will use the constructor's name and/or @@toStringTag to make
an identifiable tag for an inspected value.
Returns true if there is deep strict equality between val1 and val2.
Otherwise, returns false.
Provides a higher level API for command-line argument parsing than interacting
with process.argv directly. Takes a specification for the expected arguments
and returns a structured object with the parsed options and positionals.
Takes a function following the common error-first callback style, i.e. taking
an (err, value) => ... callback as the last argument, and returns a version
that returns promises.
Returns str with any ANSI escape codes removed.
Returns the string after replacing any surrogate code points
(or equivalently, any unpaired surrogate code units) with the
Unicode "replacement character" U+FFFD.
Creates and returns an AbortController instance whose AbortSignal is marked
as transferable and can be used with structuredClone() or postMessage().
Marks the given AbortSignal as transferable so that it can be used withstructuredClone() and postMessage().
Returns true if the value is a built-in ArrayBuffer or
SharedArrayBuffer instance.
Returns true if the value is an arguments object.
Returns true if the value is a built-in ArrayBuffer instance.
This does not include SharedArrayBuffer instances. Usually, it is
desirable to test for both; See util.types.isAnyArrayBuffer() for that.
Returns true if the value is an instance of one of the ArrayBuffer views, such as typed
array objects or DataView. Equivalent to
ArrayBuffer.isView().
Returns true if the value is an async function.
This only reports back what the JavaScript engine is seeing;
in particular, the return value may not match the original source code if
a transpilation tool was used.
Returns true if the value is a BigInt64Array instance.
Returns true if the value is a BigUint64Array instance.
Returns true if the value is a boolean object, e.g. created
by new Boolean().
Returns true if the value is any boxed primitive object, e.g. created
by new Boolean(), new String() or Object(Symbol()).
Returns true if value is a CryptoKey, false otherwise.
Returns true if the value is a built-in DataView instance.
Returns true if the value is a built-in Date instance.
Returns true if the value is a native External value.
Returns true if the value is a built-in Float32Array instance.
Returns true if the value is a built-in Float64Array instance.
Returns true if the value is a generator function.
This only reports back what the JavaScript engine is seeing;
in particular, the return value may not match the original source code if
a transpilation tool was used.
Returns true if the value is a generator object as returned from a
built-in generator function.
This only reports back what the JavaScript engine is seeing;
in particular, the return value may not match the original source code if
a transpilation tool was used.
Returns true if the value is a built-in Int16Array instance.
Returns true if the value is a built-in Int32Array instance.
Returns true if the value is a built-in Int8Array instance.
Returns true if value is a KeyObject, false otherwise.
Returns true if the value is a built-in Map instance.
Returns true if the value is an iterator returned for a built-in Map instance.
Returns true if the value is an instance of a Module Namespace Object.
Returns true if the value was returned by the constructor of a built-in Error type.
Returns true if the value is a number object, e.g. created
by new Number().
Returns true if the value is a built-in Promise.
Returns true if the value is a Proxy instance.
Returns true if the value is a regular expression object.
Returns true if the value is a built-in Set instance.
Returns true if the value is an iterator returned for a built-in Set instance.
Returns true if the value is a string object, e.g. created
by new String().
Returns true if the value is a symbol object, created
by calling Object() on a Symbol primitive.
Returns true if the value is a built-in TypedArray instance.
Returns true if the value is a built-in Uint16Array instance.
Returns true if the value is a built-in Uint32Array instance.
Returns true if the value is a built-in Uint8Array instance.
Returns true if the value is a built-in Uint8ClampedArray instance.
Returns true if the value is a built-in WeakMap instance.
Returns true if the value is a built-in WeakSet instance.
Alias for Array.isArray().
Returns true if the given object is a Boolean. Otherwise, returns false.
Returns true if the given object is a Buffer. Otherwise, returns false.
Returns true if the given object is a Date. Otherwise, returns false.
Returns true if the given object is an Error. Otherwise, returnsfalse.
Returns true if the given object is a Function. Otherwise, returnsfalse.
Returns true if the given object is strictly null. Otherwise, returnsfalse.
Returns true if the given object is null or undefined. Otherwise,
returns false.
Returns true if the given object is a Number. Otherwise, returns false.
Returns true if the given object is strictly an Objectand not aFunction (even though functions are objects in JavaScript).
Otherwise, returns false.
Returns true if the given object is a primitive type. Otherwise, returnsfalse.
Returns true if the given object is a RegExp. Otherwise, returns false.
Returns true if the given object is a string. Otherwise, returns false.
Returns true if the given object is a Symbol. Otherwise, returns false.
Returns true if the given object is undefined. Otherwise, returns false.
The util.log() method prints the given string to stdout with an included
timestamp.
That can be used to declare custom inspect functions.
Allows changing inspect settings from the repl.
That can be used to declare custom promisified variants of functions.