@@ -15,33 +15,37 @@ The module exports two specific components:
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Example using the global ` console ` :
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- console.log('hello world');
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- // Prints: hello world, to stdout
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- console.log('hello %s', 'world');
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- // Prints: hello world, to stdout
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- console.error(new Error('Whoops, something bad happened'));
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- // Prints: [Error: Whoops, something bad happened], to stderr
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-
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- const name = 'Will Robinson';
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- console.warn(`Danger ${name}! Danger!`);
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- // Prints: Danger Will Robinson! Danger!, to stderr
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+ ``` js
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+ console .log (' hello world' );
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+ // Prints: hello world, to stdout
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+ console .log (' hello %s' , ' world' );
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+ // Prints: hello world, to stdout
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+ console .error (new Error (' Whoops, something bad happened' ));
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+ // Prints: [Error: Whoops, something bad happened], to stderr
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+
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+ const name = ' Will Robinson' ;
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+ console .warn (` Danger ${ name} ! Danger!` );
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+ // Prints: Danger Will Robinson! Danger!, to stderr
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+ ```
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Example using the ` Console ` class:
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- const out = getStreamSomehow();
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- const err = getStreamSomehow();
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- const myConsole = new console.Console(out, err);
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+ ``` js
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+ const out = getStreamSomehow ();
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+ const err = getStreamSomehow ();
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+ const myConsole = new console.Console (out, err);
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- myConsole.log('hello world');
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- // Prints: hello world, to out
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- myConsole.log('hello %s', 'world');
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- // Prints: hello world, to out
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- myConsole.error(new Error('Whoops, something bad happened'));
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- // Prints: [Error: Whoops, something bad happened], to err
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+ myConsole .log (' hello world' );
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+ // Prints: hello world, to out
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+ myConsole .log (' hello %s' , ' world' );
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+ // Prints: hello world, to out
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+ myConsole .error (new Error (' Whoops, something bad happened' ));
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+ // Prints: [Error: Whoops, something bad happened], to err
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- const name = 'Will Robinson';
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- myConsole.warn(`Danger ${name}! Danger!`);
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- // Prints: Danger Will Robinson! Danger!, to err
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+ const name = ' Will Robinson' ;
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+ myConsole .warn (` Danger ${ name} ! Danger!` );
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+ // Prints: Danger Will Robinson! Danger!, to err
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+ ```
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While the API for the ` Console ` class is designed fundamentally around the
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Web browser ` console ` object, the ` Console ` is Node.js is * not* intended to
@@ -55,7 +59,9 @@ when the destination is a pipe (to avoid blocking for long periods of time).
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In the following example, stdout is non-blocking while stderr is blocking:
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- $ node script.js 2> error.log | tee info.log
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+ ```
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+ $ node script.js 2> error.log | tee info.log
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+ ```
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Typically, the distinction between blocking/non-blocking is not important
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unless an application is logging significant amounts of data. High volume
@@ -69,8 +75,10 @@ The `Console` class can be used to create a simple logger with configurable
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output streams and can be accessed using either ` require('console').Console `
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or ` console.Console ` :
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- const Console = require('console').Console;
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- const Console = console.Console;
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+ ``` js
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+ const Console = require (' console' ).Console ;
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+ const Console = console .Console ;
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+ ```
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### new Console(stdout[ , stderr] )
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@@ -79,30 +87,36 @@ Creates a new `Console` by passing one or two writable stream instances.
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is used for warning or error output. If ` stderr ` isn't passed, the warning
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and error output will be sent to the ` stdout ` .
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- const output = fs.createWriteStream('./stdout.log');
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- const errorOutput = fs.createWriteStream('./stderr.log');
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- // custom simple logger
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- const logger = new Console(output, errorOutput);
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- // use it like console
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- var count = 5;
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- logger.log('count: %d', count);
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- // in stdout.log: count 5
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+ ``` js
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+ const output = fs .createWriteStream (' ./stdout.log' );
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+ const errorOutput = fs .createWriteStream (' ./stderr.log' );
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+ // custom simple logger
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+ const logger = new Console (output, errorOutput);
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+ // use it like console
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+ var count = 5 ;
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+ logger .log (' count: %d' , count);
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+ // in stdout.log: count 5
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+ ```
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The global ` console ` is a special ` Console ` whose output is sent to
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` process.stdout ` and ` process.stderr ` . It is equivalent to calling:
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- new Console(process.stdout, process.stderr);
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+ ``` js
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+ new Console (process .stdout , process .stderr );
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+ ```
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### console.assert(value[ , message] [ , ... ] )
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A simple assertion test that verifies whether ` value ` is truthy. If it is not,
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an ` AssertionError ` is throw. If provided, the error ` message ` is formatted
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using [ ` util.format() ` ] [ ] and used as the error message.
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- console.assert(true, 'does nothing');
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- // OK
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- console.assert(false, 'Whoops %s', 'didn\'t work');
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- // AssertionError: Whoops didn't work
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+ ``` js
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+ console .assert (true , ' does nothing' );
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+ // OK
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+ console .assert (false , ' Whoops %s' , ' didn\' t work' );
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+ // AssertionError: Whoops didn't work
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+ ```
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### console.dir(obj[ , options] )
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@@ -129,11 +143,13 @@ used as the primary message and all additional used as substitution
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values similar to ` printf() ` (the arguments are all passed to
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[ ` util.format() ` ] [ ] ).
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- const code = 5;
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- console.error('error #%d', code);
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- // Prints: error #5, to stderr
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- console.error('error', code);
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- // Prints: error 5, to stderr
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+ ``` js
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+ const code = 5 ;
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+ console .error (' error #%d' , code);
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+ // Prints: error #5, to stderr
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+ console .error (' error' , code);
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+ // Prints: error 5, to stderr
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+ ```
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If formatting elements (e.g. ` %d ` ) are not found in the first string then
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[ ` util.inspect() ` ] [ ] is called on each argument and the resulting string
@@ -150,11 +166,13 @@ used as the primary message and all additional used as substitution
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values similar to ` printf() ` (the arguments are all passed to
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[ ` util.format() ` ] [ ] ).
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- var count = 5;
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- console.log('count: %d', count);
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- // Prints: count: 5, to stdout
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- console.log('count: ', count);
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- // Prints: count: 5, to stdout
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+ ``` js
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+ var count = 5 ;
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+ console .log (' count: %d' , count);
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+ // Prints: count: 5, to stdout
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+ console .log (' count: ' , count);
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+ // Prints: count: 5, to stdout
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+ ```
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If formatting elements (e.g. ` %d ` ) are not found in the first string then
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[ ` util.inspect() ` ] [ ] is called on each argument and the resulting string
@@ -172,31 +190,35 @@ milliseconds to stdout. Timer durations are accurate to the sub-millisecond.
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Stops a timer that was previously started by calling [ ` console.time() ` ] [ ] and
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prints the result to stdout:
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- console.time('100-elements');
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- for (var i = 0; i < 100; i++) {
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- ;
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- }
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- console.timeEnd('100-elements');
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- // prints 100-elements: 225.438ms
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+ ``` js
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+ console .time (' 100-elements' );
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+ for (var i = 0 ; i < 100 ; i++ ) {
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+ ;
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+ }
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+ console .timeEnd (' 100-elements' );
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+ // prints 100-elements: 225.438ms
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+ ```
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### console.trace(message[ , ...] )
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Prints to stderr the string ` 'Trace :' ` , followed by the [ ` util.format() ` ] [ ]
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formatted message and stack trace to the current position in the code.
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- console.trace('Show me');
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- // Prints: (stack trace will vary based on where trace is called)
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- // Trace: Show me
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- // at repl:2:9
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- // at REPLServer.defaultEval (repl.js:248:27)
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- // at bound (domain.js:287:14)
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- // at REPLServer.runBound [as eval] (domain.js:300:12)
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- // at REPLServer.<anonymous> (repl.js:412:12)
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- // at emitOne (events.js:82:20)
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- // at REPLServer.emit (events.js:169:7)
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- // at REPLServer.Interface._onLine (readline.js:210:10)
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- // at REPLServer.Interface._line (readline.js:549:8)
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- // at REPLServer.Interface._ttyWrite (readline.js:826:14)
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+ ``` js
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+ console .trace (' Show me' );
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+ // Prints: (stack trace will vary based on where trace is called)
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+ // Trace: Show me
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+ // at repl:2:9
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+ // at REPLServer.defaultEval (repl.js:248:27)
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+ // at bound (domain.js:287:14)
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+ // at REPLServer.runBound [as eval] (domain.js:300:12)
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+ // at REPLServer.<anonymous> (repl.js:412:12)
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+ // at emitOne (events.js:82:20)
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+ // at REPLServer.emit (events.js:169:7)
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+ // at REPLServer.Interface._onLine (readline.js:210:10)
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+ // at REPLServer.Interface._line (readline.js:549:8)
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+ // at REPLServer.Interface._ttyWrite (readline.js:826:14)
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+ ```
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### console.warn([ data] [ , ... ] )
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