Class: 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):
const { Console } = require('node:console');
const { Console } = console;
new Console(stdout[, stderr][, ignoreErrors])
#
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
.
const output = fs.createWriteStream('./stdout.log');
const errorOutput = fs.createWriteStream('./stderr.log');
const logger = new Console({ stdout: output, stderr: errorOutput });
const count = 5;
logger.log('count: %d', count);
The global console
is a special Console
whose output is sent to
process.stdout
and process.stderr
. It is equivalent to calling:
new Console({ stdout: process.stdout, stderr: process.stderr });
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.
console.assert(true, 'does nothing');
console.assert(false, 'Whoops %s work', 'didn\'t');
console.assert();
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.
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
.
> console.count()
default: 1
undefined
> console.count('default')
default: 2
undefined
> console.count('abc')
abc: 1
undefined
> console.count('xyz')
xyz: 1
undefined
> console.count('abc')
abc: 2
undefined
> console.count()
default: 3
undefined
>
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
.
> console.count('abc');
abc: 1
undefined
> console.countReset('abc');
undefined
> console.count('abc');
abc: 1
undefined
>
console.debug(data[, ...args])
#
The console.debug()
function is an alias for console.log()
.
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
.
console.dirxml(...data)
#
This method calls console.log()
passing it the arguments received.
This method does not produce any XML formatting.
console.error([data][, ...args])
#
Added in: v0.1.100
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()
).
const code = 5;
console.error('error #%d', code);
console.error('error', code);
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.
console.group([...label])
#
Added in: v8.5.0
Increases indentation of subsequent lines by spaces for groupIndentation
length.
If one or more label
s are provided, those are printed first without the
additional indentation.
console.groupCollapsed()
#
Added in: v8.5.0
An alias for console.group()
.
console.groupEnd()
#
Added in: v8.5.0
Decreases indentation of subsequent lines by spaces for groupIndentation
length.
console.info([data][, ...args])
#
Added in: v0.1.100
The console.info()
function is an alias for console.log()
.
console.log([data][, ...args])
#
Added in: v0.1.100
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()
).
const count = 5;
console.log('count: %d', count);
console.log('count:', count);
See util.format()
for more information.
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.
console.table(Symbol());
console.table(undefined);
console.table([{ a: 1, b: 'Y' }, { a: 'Z', b: 2 }]);
console.table([{ a: 1, b: 'Y' }, { a: 'Z', b: 2 }], ['a']);
console.time([label])
#
Added in: v0.1.104
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".
console.timeEnd([label])
#
Stops a timer that was previously started by calling console.time()
and
prints the result to stdout
:
console.time('bunch-of-stuff');
console.timeEnd('bunch-of-stuff');
console.timeLog([label][, ...data])
#
Added in: v10.7.0
For a timer that was previously started by calling console.time()
, prints
the elapsed time and other data
arguments to stdout
:
console.time('process');
const value = expensiveProcess1();
console.timeLog('process', value);
doExpensiveProcess2(value);
console.timeEnd('process');
console.trace([message][, ...args])
#
Added in: v0.1.104
Prints to stderr
the string 'Trace: '
, followed by the util.format()
formatted message and stack trace to the current position in the code.
console.trace('Show me');
console.warn([data][, ...args])
#
Added in: v0.1.100
The console.warn()
function is an alias for console.error()
.