Node.js v20.11.1 文档


控制台#

Console

稳定性: 2 - 稳定的

Stability: 2 - Stable

源代码: lib/console.js

node:console 模块提供了一个简单的调试控制台,类似于网络浏览器提供的 JavaScript 控制台机制。

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

该模块导出两个特定组件:

The module exports two specific components:

  • Console 类,具有 console.log()console.error()、和 console.warn() 等方法,可用于写入任何 Node.js 流。

    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.

  • 全局的 console 实例,配置为写入 process.stdoutprocess.stderr。全局的 console 无需调用 require('node:console') 就可以使用。

    A global console instance configured to write to process.stdout and process.stderr. The global console can be used without calling require('node:console').

警告:全局控制台对象的方法既不像它们类似的浏览器 API 那样始终同步,也不像所有其他 Node.js 流那样始终异步。有关详细信息,请参阅 关于进程 I/O 的注意事项

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.

使用全局的 console 的示例:

Example using the global console:

console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
//   Error: Whoops, something bad happened
//     at [eval]:5:15
//     at Script.runInThisContext (node:vm:132:18)
//     at Object.runInThisContext (node:vm:309:38)
//     at node:internal/process/execution:77:19
//     at [eval]-wrapper:6:22
//     at evalScript (node:internal/process/execution:76:60)
//     at node:internal/main/eval_string:23:3

const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr 

使用 Console 类的示例:

Example using the Console class:

const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);

myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err

const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err 

类:Console#

Class: Console

Console 类可用于创建具有可配置输出流的简单日志器,并可使用 require('node:console').Consoleconsole.Console(或它们的解构对应物)访问:

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> 写入底层流时忽略错误。默认值:true

      ignoreErrors <boolean> Ignore errors when writing to the underlying streams. Default: true.

    • colorMode <boolean> | <string> 为此 Console 实例设置颜色支持。设置为 true 可在检查值时进行着色。设置为 false 会在检查值时禁用着色。设置为 'auto' 使颜色支持取决于 isTTY 属性的值和 getColorDepth() 在相应流上返回的值。如果同时设置了 inspectOptions.colors,则无法使用此选项。默认值:'auto'

      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> 指定传给 util.inspect() 的选项。

      inspectOptions <Object> Specifies options that are passed along to util.inspect().

    • groupIndentation <number> 设置组缩进。默认值:2

      groupIndentation <number> Set group indentation. Default: 2.

使用一个或两个可写流实例创建新的 Consolestdout 是用于打印日志或信息输出的可写流。stderr 用于警告或错误输出。如果未提供 stderr,则 stdout 用于 stderr

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');
// Custom simple logger
const logger = new Console({ stdout: output, stderr: errorOutput });
// use it like console
const count = 5;
logger.log('count: %d', count);
// In stdout.log: count 5 

全局的 console 是特殊的 Console,它的输出被发送到 process.stdoutprocess.stderr。它相当于调用:

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> 测试为真的值。

    value <any> The value tested for being truthy.

  • ...message <any> 除了 value 之外的所有参数都用作错误消息。

    ...message <any> All arguments besides value are used as error message.

如果 value非真值 或省略,则 console.assert() 写入消息。它只写入一条消息,不会影响执行。输出始终以 "Assertion failed" 开头。如果提供,则使用 util.format() 格式化 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().

如果 value真值,则什么也不会发生。

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 

console.clear()#

stdout 是终端时,调用 console.clear() 将尝试清除终端。当 stdout 不是终端时,此方法不执行任何操作。

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

console.clear() 的具体操作可能因操作系统和终端类型而异。对于大多数 Linux 操作系统,console.clear() 的操作类似于 clear shell 命令。在 Windows 上,console.clear() 将仅清除 Node.js 二进制文件的当前终端视口中的输出。

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])#

  • label <string> 计数器的显示标签。默认值:'default'

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

维护一个特定于 label 的内部计数器,并向 stdout 输出使用给定 label 调用 console.count() 的次数。

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])#

  • label <string> 计数器的显示标签。默认值:'default'

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

重置特定于 label 的内部计数器。

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])#

console.debug() 函数是 console.log() 的别名。

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

console.dir(obj[, options])#

  • obj <any>

  • options <Object>

    • showHidden <boolean> 如果为 true,则对象的不可枚举和符号属性也将显示。默认值:false

      showHidden <boolean> If true then the object's non-enumerable and symbol properties will be shown too. Default: false.

    • depth <number> 告诉 util.inspect() 在格式化对象时递归多少次。这对于检查大型复杂对象很有用。要使其无限递归,则传入 null。默认值:2

      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> 如果为 true,则输出将使用 ANSI 颜色代码进行样式设置。颜色可定制;见 自定义 util.inspect() 颜色。默认值:false

      colors <boolean> If true, then the output will be styled with ANSI color codes. Colors are customizable; see customizing util.inspect() colors. Default: false.

obj 上使用 util.inspect() 并将结果字符串打印到 stdout。此函数绕过在 obj 上定义的任何自定义 inspect() 函数。

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)#

此方法调用 console.log() 将接收到的参数传给它。此方法不会产生任何 XML 格式。

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

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

使用换行符打印到 stderr。可以传递多个参数,第一个用作主要消息,所有附加参数用作类似于 printf(3) 的替换值(参数全部传递给 util.format())。

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 

如果在第一个字符串中找不到格式化元素(例如 %d),则在每个参数上调用 util.inspect() 并将结果字符串值连接起来。有关详细信息,请参阅 util.format()

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])#

将后续行的缩进增加 groupIndentation 长度的空格。

Increases indentation of subsequent lines by spaces for groupIndentation length.

如果提供了一个或多个 label,则首先打印这些 label 而无需额外缩进。

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

console.groupCollapsed()#

console.group() 的别名。

An alias for console.group().

console.groupEnd()#

将后续行的缩进减少 groupIndentation 长度的空格。

Decreases indentation of subsequent lines by spaces for groupIndentation length.

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

console.info() 函数是 console.log() 的别名。

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

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

使用换行符打印到 stdout。可以传递多个参数,第一个用作主要消息,所有附加参数用作类似于 printf(3) 的替换值(参数全部传递给 util.format())。

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 

有关详细信息,请参阅 util.format()

See util.format() for more information.

console.table(tabularData[, properties])#

  • tabularData <any>

  • properties <string[]> 用于构造表格的替代属性。

    properties <string[]> Alternate properties for constructing the table.

尝试用 tabularData 的属性的列(或使用 properties)和 tabularData 的行构建表格并记录它。如果不能将参数解析为表格,则退回到仅记录参数。

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' │
// └─────────┴─────┘ 

console.time([label])#

启动可用于计算操作持续时间的定时器。定时器由唯一的 label 标识。调用 console.timeEnd() 时使用相同的 label 停止定时器并将经过的时间以合适的时间单位输出到 stdout。例如,如果经过时间为 3869ms,则 console.timeEnd() 显示 "3.869s"。

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])#

停止之前通过调用 console.time() 启动的定时器并将结果打印到 stdout

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

console.time('bunch-of-stuff');
// Do a bunch of stuff.
console.timeEnd('bunch-of-stuff');
// Prints: bunch-of-stuff: 225.438ms 

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

对于先前通过调用 console.time() 启动的定时器,将经过时间和其他 data 参数打印到 stdout

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(); // Returns 42
console.timeLog('process', value);
// Prints "process: 365.227ms 42".
doExpensiveProcess2(value);
console.timeEnd('process'); 

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

将字符串 'Trace: ' 打印到 stderr,然后是 util.format() 格式的消息和到代码中当前位置的堆栈跟踪。

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) 

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

console.warn() 函数是 console.error() 的别名。

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

仅限检查器的方法#

Inspector only methods

以下方法由 V8 引擎在通用 API 中公开,但除非与 检查器--inspect 标志)结合使用,否则不会显示任何内容。

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).

console.profile([label])#

除非在检查器中使用,否则此方法不会显示任何内容。console.profile() 方法启动带有可选标签的 JavaScript CPU 配置文件,直到调用 console.profileEnd()。然后,该配置文件将添加到检查器的“配置文件”面板中。

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.

console.profile('MyLabel');
// Some code
console.profileEnd('MyLabel');
// Adds the profile 'MyLabel' to the Profiles panel of the inspector. 

console.profileEnd([label])#

除非在检查器中使用,否则此方法不会显示任何内容。如果当前 JavaScript CPU 分析会话已启动,则停止当前 JavaScript CPU 分析会话,并将报告打印到检查器的“配置文件”面板。有关示例,请参见 console.profile()

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.

如果在没有标签的情况下调用此方法,则会停止最近启动的配置文件。

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

console.timeStamp([label])#

除非在检查器中使用,否则此方法不会显示任何内容。console.timeStamp() 方法将带有标签 'label' 的事件添加到检查器的“时间轴”面板。

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.