Console

Added in: v0.10.13

源代码: lib/console.js

The node:console module provides a simple debugging console that is similar to the JavaScript console mechanism provided by web browsers.

The module exports two specific components:

• A Console class with methods such as console.log(), console.error(), and console.warn() that can be used to write to any Node.js stream.
• A global console instance configured to write to process.stdout and process.stderr. The global console can be used without calling require('node:console').

Warning: The global console object's methods are neither consistently synchronous like the browser APIs they resemble, nor are they consistently asynchronous like all other Node.js streams. See the note on process I/O for more information.

Example using the global console:

JScopy

Example using the Console class:

JScopy

C Console

The Console class can be used to create a simple logger with configurable output streams and can be accessed using either require('node:console').Console or console.Console (or their destructured counterparts):

JScopy

JScopy

M new Console(stdout[, stderr][, ignoreErrors])

M new Console(options)

• options Object
  • stdout stream.Writable
  • stderr stream.Writable
  • ignoreErrors boolean Ignore errors when writing to the underlying streams. Default: true.
  • colorMode boolean | string Set color support for this Console instance. Setting to true enables coloring while inspecting values. Setting to false disables coloring while inspecting values. Setting to 'auto' makes color support depend on the value of the isTTY property and the value returned by getColorDepth() on the respective stream. This option can not be used, if inspectOptions.colors is set as well. Default: 'auto'.
  • inspectOptions Object Specifies options that are passed along to util.inspect().
  • groupIndentation number Set group indentation. Default: 2.

Creates a new Console with one or two writable stream instances. stdout is a writable stream to print log or info output. stderr is used for warning or error output. If stderr is not provided, stdout is used for stderr.

JScopy

The global console is a special Console whose output is sent to process.stdout and process.stderr. It is equivalent to calling:

JScopy

M console.assert(value[, ...message])

• value any The value tested for being truthy.
• ...message any All arguments besides value are used as error message.

console.assert() writes a message if value is falsy or omitted. It only writes a message and does not otherwise affect execution. The output always starts with "Assertion failed". If provided, message is formatted using util.format().

If value is truthy, nothing happens.

JScopy

M console.clear()

Added in: v8.3.0

When stdout is a TTY, calling console.clear() will attempt to clear the TTY. When stdout is not a TTY, this method does nothing.

The specific operation of console.clear() can vary across operating systems and terminal types. For most Linux operating systems, console.clear() operates similarly to the clear shell command. On Windows, console.clear() will clear only the output in the current terminal viewport for the Node.js binary.

M console.count([label])

Added in: v8.3.0

• label string The display label for the counter. Default: 'default'.

Maintains an internal counter specific to label and outputs to stdout the number of times console.count() has been called with the given label.

JScopy

M console.countReset([label])

Added in: v8.3.0

• label string The display label for the counter. Default: 'default'.

Resets the internal counter specific to label.

JScopy

M console.debug(data[, ...args])

• data any
• ...args any

The console.debug() function is an alias for console.log().

M console.dir(obj[, options])

Added in: v0.1.101

• obj any
• options Object
  • showHidden boolean If true then the object's non-enumerable and symbol properties will be shown too. Default: false.
  • depth number Tells util.inspect() how many times to recurse while formatting the object. This is useful for inspecting large complicated objects. To make it recurse indefinitely, pass null. Default: 2.
  • colors boolean If true, then the output will be styled with ANSI color codes. Colors are customizable; see customizing util.inspect() colors. Default: false.

Uses util.inspect() on obj and prints the resulting string to stdout. This function bypasses any custom inspect() function defined on obj.

M console.dirxml(...data)

• ...data any

This method calls console.log() passing it the arguments received. This method does not produce any XML formatting.

M console.error([data][, ...args])

Added in: v0.1.100

• data any
• ...args any

Prints to stderr with newline. Multiple arguments can be passed, with the first used as the primary message and all additional used as substitution values similar to printf(3) (the arguments are all passed to util.format()).

JScopy

If formatting elements (e.g. %d) are not found in the first string then util.inspect() is called on each argument and the resulting string values are concatenated. See util.format() for more information.

M console.group([...label])

Added in: v8.5.0

• ...label any

Increases indentation of subsequent lines by spaces for groupIndentation length.

If one or more labels are provided, those are printed first without the additional indentation.

M console.groupCollapsed()

Added in: v8.5.0

An alias for console.group().

M console.groupEnd()

Added in: v8.5.0

Decreases indentation of subsequent lines by spaces for groupIndentation length.

M console.info([data][, ...args])

Added in: v0.1.100

• data any
• ...args any

The console.info() function is an alias for console.log().

M console.log([data][, ...args])

Added in: v0.1.100

• data any
• ...args any

Prints to stdout with newline. Multiple arguments can be passed, with the first used as the primary message and all additional used as substitution values similar to printf(3) (the arguments are all passed to util.format()).

JScopy

See util.format() for more information.

M console.table(tabularData[, properties])

Added in: v10.0.0

• tabularData any
• properties string[] Alternate properties for constructing the table.

Try to construct a table with the columns of the properties of tabularData (or use properties) and rows of tabularData and log it. Falls back to just logging the argument if it can't be parsed as tabular.

JScopy

M console.time([label])

Added in: v0.1.104

• label string Default: 'default'

Starts a timer that can be used to compute the duration of an operation. Timers are identified by a unique label. Use the same label when calling console.timeEnd() to stop the timer and output the elapsed time in suitable time units to stdout. For example, if the elapsed time is 3869ms, console.timeEnd() displays "3.869s".

M console.timeEnd([label])

• label string Default: 'default'

Stops a timer that was previously started by calling console.time() and prints the result to stdout:

JScopy

M console.timeLog([label][, ...data])

Added in: v10.7.0

• label string Default: 'default'
• ...data any

For a timer that was previously started by calling console.time(), prints the elapsed time and other data arguments to stdout:

JScopy

M console.trace([message][, ...args])

Added in: v0.1.104

• message any
• ...args any

Prints to stderr the string 'Trace: ', followed by the util.format() formatted message and stack trace to the current position in the code.

JScopy

M console.warn([data][, ...args])

Added in: v0.1.100

• data any
• ...args any

The console.warn() function is an alias for console.error().

Inspector only methods

The following methods are exposed by the V8 engine in the general API but do not display anything unless used in conjunction with the inspector (--inspect flag).

M console.profile([label])

Added in: v8.0.0

• label string

This method does not display anything unless used in the inspector. The console.profile() method starts a JavaScript CPU profile with an optional label until console.profileEnd() is called. The profile is then added to the Profile panel of the inspector.

JScopy

M console.profileEnd([label])

Added in: v8.0.0

• label string

This method does not display anything unless used in the inspector. Stops the current JavaScript CPU profiling session if one has been started and prints the report to the Profiles panel of the inspector. See console.profile() for an example.

If this method is called without a label, the most recently started profile is stopped.

M console.timeStamp([label])

Added in: v8.0.0

• label string

This method does not display anything unless used in the inspector. The console.timeStamp() method adds an event with the label 'label' to the Timeline panel of the inspector.