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');
// Assertion failed: Whoops didn't work
console.assert();
// Assertion failed
The value tested for being truthy.
All arguments besides value are used as error message.
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.
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
>
The display label for the counter.
Resets the internal counter specific to label.
> console.count('abc');
abc: 1
undefined
> console.countReset('abc');
undefined
> console.count('abc');
abc: 1
undefined
>
The display label for the counter.
The console.debug() function is an alias for log.
Uses util.inspect() on obj and prints the resulting string to stdout.
This function bypasses any custom inspect() function defined on obj.
This method calls console.log() passing it the arguments received.
This method does not produce any XML formatting.
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);
// Prints: error #5, to stderr
console.error('error', code);
// Prints: error 5, to stderr
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.
Increases indentation of subsequent lines by spaces for groupIndentationlength.
If one or more labels are provided, those are printed first without the
additional indentation.
An alias for group.
Decreases indentation of subsequent lines by spaces for groupIndentationlength.
The console.info() function is an alias for log.
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);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format() for more information.
This method does not display anything unless used in the inspector. Starts a JavaScript CPU profile with an optional label.
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.
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.
// These can't be parsed as tabular data
console.table(Symbol());
// Symbol()
console.table(undefined);
// undefined
console.table([{ a: 1, b: 'Y' }, { a: 'Z', b: 2 }]);
// ┌─────────┬─────┬─────┐
// │ (index) │ a │ b │
// ├─────────┼─────┼─────┤
// │ 0 │ 1 │ 'Y' │
// │ 1 │ 'Z' │ 2 │
// └─────────┴─────┴─────┘
console.table([{ a: 1, b: 'Y' }, { a: 'Z', b: 2 }], ['a']);
// ┌─────────┬─────┐
// │ (index) │ a │
// ├─────────┼─────┤
// │ 0 │ 1 │
// │ 1 │ 'Z' │
// └─────────┴─────┘
Alternate properties for constructing the table.
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 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".
Stops a timer that was previously started by calling time and
prints the result to stdout:
console.time('100-elements');
for (let i = 0; i < 100; i++) {}
console.timeEnd('100-elements');
// prints 100-elements: 225.438ms
For a timer that was previously started by calling time, prints
the elapsed time and other data arguments to stdout:
console.time('process');
const value = expensiveProcess1(); // Returns 42
console.timeLog('process', value);
// Prints "process: 365.227ms 42".
doExpensiveProcess2(value);
console.timeEnd('process');
This method does not display anything unless used in the inspector.
Adds an event with the label label to the Timeline panel of the inspector.
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');
// Prints: (stack trace will vary based on where trace is called)
// Trace: Show me
// at repl:2:9
// at REPLServer.defaultEval (repl.js:248:27)
// at bound (domain.js:287:14)
// at REPLServer.runBound [as eval] (domain.js:300:12)
// at REPLServer.<anonymous> (repl.js:412:12)
// at emitOne (events.js:82:20)
// at REPLServer.emit (events.js:169:7)
// at REPLServer.Interface._onLine (readline.js:210:10)
// at REPLServer.Interface._line (readline.js:549:8)
// at REPLServer.Interface._ttyWrite (readline.js:826:14)
The console.warn() function is an alias for error.
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