The module exports a console object, whose output is sent to stdout or stderr.

For ease of use, console is defined as a global object and can be used
directly without require.


Ruff available: v1.6.0

  • {Object}

For printing to stdout and stderr. Similar to the console object functions
provided by most web browsers, here the output is sent to stdout or stderr.

The console functions are synchronous when the destination is a terminal or
a file (to avoid lost messages in case of premature exit) and asynchronous
when it’s a pipe (to avoid blocking for long periods of time).

In daily use, the blocking/non-blocking dichotomy is not something you
should worry about unless you log huge amounts of data.

console.log([data][, …])

Ruff available: v1.6.0

Prints to stdout with newline. This function can take multiple arguments in a
printf()-like way. Example:

var count = 5;
console.log('count: %d', count);
// prints 'count: 5'

If formatting elements are not found in the first string then util.inspect
is used on each argument. See [util.format()][] for more information.[data][, …])

Ruff available: v1.6.0

Same as console.log.

console.error([data][, …])

Ruff available: v1.6.0

Same as console.log but prints to stderr.

console.warn([data][, …])

Ruff available: v1.6.0

Same as console.error.

console.dir(obj[, options])

Ruff available: v1.6.0

Uses util.inspect on obj and prints resulting string to stdout. This function
bypasses any custom inspect() function on obj. An optional options object
may be passed that alters certain aspects of the formatted string:

  • showHidden - if true then the object’s non-enumerable and symbol
    properties will be shown too. Defaults to false.

  • depth - tells inspect how many times to recurse while formatting the
    object. This is useful for inspecting large complicated objects. Defaults to
    2. To make it recurse indefinitely pass null.

  • colors - if true, then the output will be styled with ANSI color codes.
    Defaults to false. Colors are customizable, see [util.inspect()] for more information.


Ruff available: v1.6.0

Used to calculate the duration of a specific operation. To start a timer, call
the console.time() method, giving it a name as only parameter. To stop the
timer, and to get the elapsed time in milliseconds, just call the
console.timeEnd() method, again passing the
timer’s name as the parameter.


Ruff available: v1.6.0

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


for (var i = 0; i < 100; i++) {
// prints 100-elements: 262ms

console.trace(message[, …])

Ruff available: v1.6.0

Print to stderr 'Trace :', followed by the formatted message and stack trace
to the current position.

console.assert(value[, message][, …])

Ruff available: v1.6.0

Similar to [assert.ok()][], but the error message is formatted as