{ "type": "module", "source": "doc/api/console.md", "modules": [ { "textRaw": "Console", "name": "console", "introduced_in": "v0.10.13", "stability": 2, "stabilityText": "Stable", "desc": "<p><strong>Source Code:</strong> <a href=\"https://github.com/nodejs/node/blob/v16.20.2/lib/console.js\">lib/console.js</a></p>\n<p>The <code>node:console</code> module provides a simple debugging console that is similar to\nthe JavaScript console mechanism provided by web browsers.</p>\n<p>The module exports two specific components:</p>\n<ul>\n<li>A <code>Console</code> class with methods such as <code>console.log()</code>, <code>console.error()</code>, and\n<code>console.warn()</code> that can be used to write to any Node.js stream.</li>\n<li>A global <code>console</code> instance configured to write to <a href=\"process.html#processstdout\"><code>process.stdout</code></a> and\n<a href=\"process.html#processstderr\"><code>process.stderr</code></a>. The global <code>console</code> can be used without calling\n<code>require('node:console')</code>.</li>\n</ul>\n<p><em><strong>Warning</strong></em>: The global console object's methods are neither consistently\nsynchronous like the browser APIs they resemble, nor are they consistently\nasynchronous like all other Node.js streams. See the <a href=\"process.html#a-note-on-process-io\">note on process I/O</a> for\nmore information.</p>\n<p>Example using the global <code>console</code>:</p>\n<pre><code class=\"language-js\">console.log('hello world');\n// Prints: hello world, to stdout\nconsole.log('hello %s', 'world');\n// Prints: hello world, to stdout\nconsole.error(new Error('Whoops, something bad happened'));\n// Prints error message and stack trace to stderr:\n// Error: Whoops, something bad happened\n// at [eval]:5:15\n// at Script.runInThisContext (node:vm:132:18)\n// at Object.runInThisContext (node:vm:309:38)\n// at node:internal/process/execution:77:19\n// at [eval]-wrapper:6:22\n// at evalScript (node:internal/process/execution:76:60)\n// at node:internal/main/eval_string:23:3\n\nconst name = 'Will Robinson';\nconsole.warn(`Danger ${name}! Danger!`);\n// Prints: Danger Will Robinson! Danger!, to stderr\n</code></pre>\n<p>Example using the <code>Console</code> class:</p>\n<pre><code class=\"language-js\">const out = getStreamSomehow();\nconst err = getStreamSomehow();\nconst myConsole = new console.Console(out, err);\n\nmyConsole.log('hello world');\n// Prints: hello world, to out\nmyConsole.log('hello %s', 'world');\n// Prints: hello world, to out\nmyConsole.error(new Error('Whoops, something bad happened'));\n// Prints: [Error: Whoops, something bad happened], to err\n\nconst name = 'Will Robinson';\nmyConsole.warn(`Danger ${name}! Danger!`);\n// Prints: Danger Will Robinson! Danger!, to err\n</code></pre>", "classes": [ { "textRaw": "Class: `Console`", "type": "class", "name": "Console", "meta": { "changes": [ { "version": "v8.0.0", "pr-url": "https://github.com/nodejs/node/pull/9744", "description": "Errors that occur while writing to the underlying streams will now be ignored by default." } ] }, "desc": "<p>The <code>Console</code> class can be used to create a simple logger with configurable\noutput streams and can be accessed using either <code>require('node:console').Console</code>\nor <code>console.Console</code> (or their destructured counterparts):</p>\n<pre><code class=\"language-js\">const { Console } = require('node:console');\n</code></pre>\n<pre><code class=\"language-js\">const { Console } = console;\n</code></pre>", "methods": [ { "textRaw": "`console.assert(value[, ...message])`", "type": "method", "name": "assert", "meta": { "added": [ "v0.1.101" ], "changes": [ { "version": "v10.0.0", "pr-url": "https://github.com/nodejs/node/pull/17706", "description": "The implementation is now spec compliant and does not throw anymore." } ] }, "signatures": [ { "params": [ { "textRaw": "`value` {any} The value tested for being truthy.", "name": "value", "type": "any", "desc": "The value tested for being truthy." }, { "textRaw": "`...message` {any} All arguments besides `value` are used as error message.", "name": "...message", "type": "any", "desc": "All arguments besides `value` are used as error message." } ] } ], "desc": "<p><code>console.assert()</code> writes a message if <code>value</code> is <a href=\"https://developer.mozilla.org/en-US/docs/Glossary/Falsy\">falsy</a> or omitted. It only\nwrites a message and does not otherwise affect execution. The output always\nstarts with <code>\"Assertion failed\"</code>. If provided, <code>message</code> is formatted using\n<a href=\"util.html#utilformatformat-args\"><code>util.format()</code></a>.</p>\n<p>If <code>value</code> is <a href=\"https://developer.mozilla.org/en-US/docs/Glossary/Truthy\">truthy</a>, nothing happens.</p>\n<pre><code class=\"language-js\">console.assert(true, 'does nothing');\n\nconsole.assert(false, 'Whoops %s work', 'didn\\'t');\n// Assertion failed: Whoops didn't work\n\nconsole.assert();\n// Assertion failed\n</code></pre>" }, { "textRaw": "`console.clear()`", "type": "method", "name": "clear", "meta": { "added": [ "v8.3.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "<p>When <code>stdout</code> is a TTY, calling <code>console.clear()</code> will attempt to clear the\nTTY. When <code>stdout</code> is not a TTY, this method does nothing.</p>\n<p>The specific operation of <code>console.clear()</code> can vary across operating systems\nand terminal types. For most Linux operating systems, <code>console.clear()</code>\noperates similarly to the <code>clear</code> shell command. On Windows, <code>console.clear()</code>\nwill clear only the output in the current terminal viewport for the Node.js\nbinary.</p>" }, { "textRaw": "`console.count([label])`", "type": "method", "name": "count", "meta": { "added": [ "v8.3.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`label` {string} The display label for the counter. **Default:** `'default'`.", "name": "label", "type": "string", "default": "`'default'`", "desc": "The display label for the counter." } ] } ], "desc": "<p>Maintains an internal counter specific to <code>label</code> and outputs to <code>stdout</code> the\nnumber of times <code>console.count()</code> has been called with the given <code>label</code>.</p>\n<!-- eslint-skip -->\n<pre><code class=\"language-js\">> console.count()\ndefault: 1\nundefined\n> console.count('default')\ndefault: 2\nundefined\n> console.count('abc')\nabc: 1\nundefined\n> console.count('xyz')\nxyz: 1\nundefined\n> console.count('abc')\nabc: 2\nundefined\n> console.count()\ndefault: 3\nundefined\n>\n</code></pre>" }, { "textRaw": "`console.countReset([label])`", "type": "method", "name": "countReset", "meta": { "added": [ "v8.3.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`label` {string} The display label for the counter. **Default:** `'default'`.", "name": "label", "type": "string", "default": "`'default'`", "desc": "The display label for the counter." } ] } ], "desc": "<p>Resets the internal counter specific to <code>label</code>.</p>\n<!-- eslint-skip -->\n<pre><code class=\"language-js\">> console.count('abc');\nabc: 1\nundefined\n> console.countReset('abc');\nundefined\n> console.count('abc');\nabc: 1\nundefined\n>\n</code></pre>" }, { "textRaw": "`console.debug(data[, ...args])`", "type": "method", "name": "debug", "meta": { "added": [ "v8.0.0" ], "changes": [ { "version": "v8.10.0", "pr-url": "https://github.com/nodejs/node/pull/17033", "description": "`console.debug` is now an alias for `console.log`." } ] }, "signatures": [ { "params": [ { "textRaw": "`data` {any}", "name": "data", "type": "any" }, { "textRaw": "`...args` {any}", "name": "...args", "type": "any" } ] } ], "desc": "<p>The <code>console.debug()</code> function is an alias for <a href=\"#consolelogdata-args\"><code>console.log()</code></a>.</p>" }, { "textRaw": "`console.dir(obj[, options])`", "type": "method", "name": "dir", "meta": { "added": [ "v0.1.101" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`obj` {any}", "name": "obj", "type": "any" }, { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`showHidden` {boolean} If `true` then the object's non-enumerable and symbol properties will be shown too. **Default:** `false`.", "name": "showHidden", "type": "boolean", "default": "`false`", "desc": "If `true` then the object's non-enumerable and symbol properties will be shown too." }, { "textRaw": "`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`.", "name": "depth", "type": "number", "default": "`2`", "desc": "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`." }, { "textRaw": "`colors` {boolean} If `true`, then the output will be styled with ANSI color codes. Colors are customizable; see [customizing `util.inspect()` colors][]. **Default:** `false`.", "name": "colors", "type": "boolean", "default": "`false`", "desc": "If `true`, then the output will be styled with ANSI color codes. Colors are customizable; see [customizing `util.inspect()` colors][]." } ] } ] } ], "desc": "<p>Uses <a href=\"util.html#utilinspectobject-options\"><code>util.inspect()</code></a> on <code>obj</code> and prints the resulting string to <code>stdout</code>.\nThis function bypasses any custom <code>inspect()</code> function defined on <code>obj</code>.</p>" }, { "textRaw": "`console.dirxml(...data)`", "type": "method", "name": "dirxml", "meta": { "added": [ "v8.0.0" ], "changes": [ { "version": "v9.3.0", "pr-url": "https://github.com/nodejs/node/pull/17152", "description": "`console.dirxml` now calls `console.log` for its arguments." } ] }, "signatures": [ { "params": [ { "textRaw": "`...data` {any}", "name": "...data", "type": "any" } ] } ], "desc": "<p>This method calls <code>console.log()</code> passing it the arguments received.\nThis method does not produce any XML formatting.</p>" }, { "textRaw": "`console.error([data][, ...args])`", "type": "method", "name": "error", "meta": { "added": [ "v0.1.100" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`data` {any}", "name": "data", "type": "any" }, { "textRaw": "`...args` {any}", "name": "...args", "type": "any" } ] } ], "desc": "<p>Prints to <code>stderr</code> with newline. Multiple arguments can be passed, with the\nfirst used as the primary message and all additional used as substitution\nvalues similar to <a href=\"http://man7.org/linux/man-pages/man3/printf.3.html\"><code>printf(3)</code></a> (the arguments are all passed to\n<a href=\"util.html#utilformatformat-args\"><code>util.format()</code></a>).</p>\n<pre><code class=\"language-js\">const code = 5;\nconsole.error('error #%d', code);\n// Prints: error #5, to stderr\nconsole.error('error', code);\n// Prints: error 5, to stderr\n</code></pre>\n<p>If formatting elements (e.g. <code>%d</code>) are not found in the first string then\n<a href=\"util.html#utilinspectobject-options\"><code>util.inspect()</code></a> is called on each argument and the resulting string\nvalues are concatenated. See <a href=\"util.html#utilformatformat-args\"><code>util.format()</code></a> for more information.</p>" }, { "textRaw": "`console.group([...label])`", "type": "method", "name": "group", "meta": { "added": [ "v8.5.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`...label` {any}", "name": "...label", "type": "any" } ] } ], "desc": "<p>Increases indentation of subsequent lines by spaces for <code>groupIndentation</code>\nlength.</p>\n<p>If one or more <code>label</code>s are provided, those are printed first without the\nadditional indentation.</p>" }, { "textRaw": "`console.groupCollapsed()`", "type": "method", "name": "groupCollapsed", "meta": { "added": [ "v8.5.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "<p>An alias for <a href=\"#consolegrouplabel\"><code>console.group()</code></a>.</p>" }, { "textRaw": "`console.groupEnd()`", "type": "method", "name": "groupEnd", "meta": { "added": [ "v8.5.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "<p>Decreases indentation of subsequent lines by spaces for <code>groupIndentation</code>\nlength.</p>" }, { "textRaw": "`console.info([data][, ...args])`", "type": "method", "name": "info", "meta": { "added": [ "v0.1.100" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`data` {any}", "name": "data", "type": "any" }, { "textRaw": "`...args` {any}", "name": "...args", "type": "any" } ] } ], "desc": "<p>The <code>console.info()</code> function is an alias for <a href=\"#consolelogdata-args\"><code>console.log()</code></a>.</p>" }, { "textRaw": "`console.log([data][, ...args])`", "type": "method", "name": "log", "meta": { "added": [ "v0.1.100" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`data` {any}", "name": "data", "type": "any" }, { "textRaw": "`...args` {any}", "name": "...args", "type": "any" } ] } ], "desc": "<p>Prints to <code>stdout</code> with newline. Multiple arguments can be passed, with the\nfirst used as the primary message and all additional used as substitution\nvalues similar to <a href=\"http://man7.org/linux/man-pages/man3/printf.3.html\"><code>printf(3)</code></a> (the arguments are all passed to\n<a href=\"util.html#utilformatformat-args\"><code>util.format()</code></a>).</p>\n<pre><code class=\"language-js\">const count = 5;\nconsole.log('count: %d', count);\n// Prints: count: 5, to stdout\nconsole.log('count:', count);\n// Prints: count: 5, to stdout\n</code></pre>\n<p>See <a href=\"util.html#utilformatformat-args\"><code>util.format()</code></a> for more information.</p>" }, { "textRaw": "`console.table(tabularData[, properties])`", "type": "method", "name": "table", "meta": { "added": [ "v10.0.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`tabularData` {any}", "name": "tabularData", "type": "any" }, { "textRaw": "`properties` {string\\[]} Alternate properties for constructing the table.", "name": "properties", "type": "string\\[]", "desc": "Alternate properties for constructing the table." } ] } ], "desc": "<p>Try to construct a table with the columns of the properties of <code>tabularData</code>\n(or use <code>properties</code>) and rows of <code>tabularData</code> and log it. Falls back to just\nlogging the argument if it can't be parsed as tabular.</p>\n<pre><code class=\"language-js\">// These can't be parsed as tabular data\nconsole.table(Symbol());\n// Symbol()\n\nconsole.table(undefined);\n// undefined\n\nconsole.table([{ a: 1, b: 'Y' }, { a: 'Z', b: 2 }]);\n// ┌─────────┬─────┬─────┐\n// │ (index) │ a │ b │\n// ├─────────┼─────┼─────┤\n// │ 0 │ 1 │ 'Y' │\n// │ 1 │ 'Z' │ 2 │\n// └─────────┴─────┴─────┘\n\nconsole.table([{ a: 1, b: 'Y' }, { a: 'Z', b: 2 }], ['a']);\n// ┌─────────┬─────┐\n// │ (index) │ a │\n// ├─────────┼─────┤\n// │ 0 │ 1 │\n// │ 1 │ 'Z' │\n// └─────────┴─────┘\n</code></pre>" }, { "textRaw": "`console.time([label])`", "type": "method", "name": "time", "meta": { "added": [ "v0.1.104" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`label` {string} **Default:** `'default'`", "name": "label", "type": "string", "default": "`'default'`" } ] } ], "desc": "<p>Starts a timer that can be used to compute the duration of an operation. Timers\nare identified by a unique <code>label</code>. Use the same <code>label</code> when calling\n<a href=\"#consoletimeendlabel\"><code>console.timeEnd()</code></a> to stop the timer and output the elapsed time in\nsuitable time units to <code>stdout</code>. For example, if the elapsed\ntime is 3869ms, <code>console.timeEnd()</code> displays \"3.869s\".</p>" }, { "textRaw": "`console.timeEnd([label])`", "type": "method", "name": "timeEnd", "meta": { "added": [ "v0.1.104" ], "changes": [ { "version": "v13.0.0", "pr-url": "https://github.com/nodejs/node/pull/29251", "description": "The elapsed time is displayed with a suitable time unit." }, { "version": "v6.0.0", "pr-url": "https://github.com/nodejs/node/pull/5901", "description": "This method no longer supports multiple calls that don't map to individual `console.time()` calls; see below for details." } ] }, "signatures": [ { "params": [ { "textRaw": "`label` {string} **Default:** `'default'`", "name": "label", "type": "string", "default": "`'default'`" } ] } ], "desc": "<p>Stops a timer that was previously started by calling <a href=\"#consoletimelabel\"><code>console.time()</code></a> and\nprints the result to <code>stdout</code>:</p>\n<pre><code class=\"language-js\">console.time('bunch-of-stuff');\n// Do a bunch of stuff.\nconsole.timeEnd('bunch-of-stuff');\n// Prints: bunch-of-stuff: 225.438ms\n</code></pre>" }, { "textRaw": "`console.timeLog([label][, ...data])`", "type": "method", "name": "timeLog", "meta": { "added": [ "v10.7.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`label` {string} **Default:** `'default'`", "name": "label", "type": "string", "default": "`'default'`" }, { "textRaw": "`...data` {any}", "name": "...data", "type": "any" } ] } ], "desc": "<p>For a timer that was previously started by calling <a href=\"#consoletimelabel\"><code>console.time()</code></a>, prints\nthe elapsed time and other <code>data</code> arguments to <code>stdout</code>:</p>\n<pre><code class=\"language-js\">console.time('process');\nconst value = expensiveProcess1(); // Returns 42\nconsole.timeLog('process', value);\n// Prints \"process: 365.227ms 42\".\ndoExpensiveProcess2(value);\nconsole.timeEnd('process');\n</code></pre>" }, { "textRaw": "`console.trace([message][, ...args])`", "type": "method", "name": "trace", "meta": { "added": [ "v0.1.104" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`message` {any}", "name": "message", "type": "any" }, { "textRaw": "`...args` {any}", "name": "...args", "type": "any" } ] } ], "desc": "<p>Prints to <code>stderr</code> the string <code>'Trace: '</code>, followed by the <a href=\"util.html#utilformatformat-args\"><code>util.format()</code></a>\nformatted message and stack trace to the current position in the code.</p>\n<pre><code class=\"language-js\">console.trace('Show me');\n// Prints: (stack trace will vary based on where trace is called)\n// Trace: Show me\n// at repl:2:9\n// at REPLServer.defaultEval (repl.js:248:27)\n// at bound (domain.js:287:14)\n// at REPLServer.runBound [as eval] (domain.js:300:12)\n// at REPLServer.&#x3C;anonymous> (repl.js:412:12)\n// at emitOne (events.js:82:20)\n// at REPLServer.emit (events.js:169:7)\n// at REPLServer.Interface._onLine (readline.js:210:10)\n// at REPLServer.Interface._line (readline.js:549:8)\n// at REPLServer.Interface._ttyWrite (readline.js:826:14)\n</code></pre>" }, { "textRaw": "`console.warn([data][, ...args])`", "type": "method", "name": "warn", "meta": { "added": [ "v0.1.100" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`data` {any}", "name": "data", "type": "any" }, { "textRaw": "`...args` {any}", "name": "...args", "type": "any" } ] } ], "desc": "<p>The <code>console.warn()</code> function is an alias for <a href=\"#consoleerrordata-args\"><code>console.error()</code></a>.</p>" } ], "signatures": [ { "params": [ { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`stdout` {stream.Writable}", "name": "stdout", "type": "stream.Writable" }, { "textRaw": "`stderr` {stream.Writable}", "name": "stderr", "type": "stream.Writable" }, { "textRaw": "`ignoreErrors` {boolean} Ignore errors when writing to the underlying streams. **Default:** `true`.", "name": "ignoreErrors", "type": "boolean", "default": "`true`", "desc": "Ignore errors when writing to the underlying streams." }, { "textRaw": "`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'`.", "name": "colorMode", "type": "boolean|string", "default": "`'auto'`", "desc": "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." }, { "textRaw": "`inspectOptions` {Object} Specifies options that are passed along to [`util.inspect()`][].", "name": "inspectOptions", "type": "Object", "desc": "Specifies options that are passed along to [`util.inspect()`][]." }, { "textRaw": "`groupIndentation` {number} Set group indentation. **Default:** `2`.", "name": "groupIndentation", "type": "number", "default": "`2`", "desc": "Set group indentation." } ] } ], "desc": "<p>Creates a new <code>Console</code> with one or two writable stream instances. <code>stdout</code> is a\nwritable stream to print log or info output. <code>stderr</code> is used for warning or\nerror output. If <code>stderr</code> is not provided, <code>stdout</code> is used for <code>stderr</code>.</p>\n<pre><code class=\"language-js\">const output = fs.createWriteStream('./stdout.log');\nconst errorOutput = fs.createWriteStream('./stderr.log');\n// Custom simple logger\nconst logger = new Console({ stdout: output, stderr: errorOutput });\n// use it like console\nconst count = 5;\nlogger.log('count: %d', count);\n// In stdout.log: count 5\n</code></pre>\n<p>The global <code>console</code> is a special <code>Console</code> whose output is sent to\n<a href=\"process.html#processstdout\"><code>process.stdout</code></a> and <a href=\"process.html#processstderr\"><code>process.stderr</code></a>. It is equivalent to calling:</p>\n<pre><code class=\"language-js\">new Console({ stdout: process.stdout, stderr: process.stderr });\n</code></pre>" }, { "params": [ { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`stdout` {stream.Writable}", "name": "stdout", "type": "stream.Writable" }, { "textRaw": "`stderr` {stream.Writable}", "name": "stderr", "type": "stream.Writable" }, { "textRaw": "`ignoreErrors` {boolean} Ignore errors when writing to the underlying streams. **Default:** `true`.", "name": "ignoreErrors", "type": "boolean", "default": "`true`", "desc": "Ignore errors when writing to the underlying streams." }, { "textRaw": "`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'`.", "name": "colorMode", "type": "boolean|string", "default": "`'auto'`", "desc": "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." }, { "textRaw": "`inspectOptions` {Object} Specifies options that are passed along to [`util.inspect()`][].", "name": "inspectOptions", "type": "Object", "desc": "Specifies options that are passed along to [`util.inspect()`][]." }, { "textRaw": "`groupIndentation` {number} Set group indentation. **Default:** `2`.", "name": "groupIndentation", "type": "number", "default": "`2`", "desc": "Set group indentation." } ] } ], "desc": "<p>Creates a new <code>Console</code> with one or two writable stream instances. <code>stdout</code> is a\nwritable stream to print log or info output. <code>stderr</code> is used for warning or\nerror output. If <code>stderr</code> is not provided, <code>stdout</code> is used for <code>stderr</code>.</p>\n<pre><code class=\"language-js\">const output = fs.createWriteStream('./stdout.log');\nconst errorOutput = fs.createWriteStream('./stderr.log');\n// Custom simple logger\nconst logger = new Console({ stdout: output, stderr: errorOutput });\n// use it like console\nconst count = 5;\nlogger.log('count: %d', count);\n// In stdout.log: count 5\n</code></pre>\n<p>The global <code>console</code> is a special <code>Console</code> whose output is sent to\n<a href=\"process.html#processstdout\"><code>process.stdout</code></a> and <a href=\"process.html#processstderr\"><code>process.stderr</code></a>. It is equivalent to calling:</p>\n<pre><code class=\"language-js\">new Console({ stdout: process.stdout, stderr: process.stderr });\n</code></pre>" } ] } ], "modules": [ { "textRaw": "Inspector only methods", "name": "inspector_only_methods", "desc": "<p>The following methods are exposed by the V8 engine in the general API but do\nnot display anything unless used in conjunction with the <a href=\"debugger.html\">inspector</a>\n(<code>--inspect</code> flag).</p>", "methods": [ { "textRaw": "`console.profile([label])`", "type": "method", "name": "profile", "meta": { "added": [ "v8.0.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`label` {string}", "name": "label", "type": "string" } ] } ], "desc": "<p>This method does not display anything unless used in the inspector. The\n<code>console.profile()</code> method starts a JavaScript CPU profile with an optional\nlabel until <a href=\"#consoleprofileendlabel\"><code>console.profileEnd()</code></a> is called. The profile is then added to\nthe <strong>Profile</strong> panel of the inspector.</p>\n<pre><code class=\"language-js\">console.profile('MyLabel');\n// Some code\nconsole.profileEnd('MyLabel');\n// Adds the profile 'MyLabel' to the Profiles panel of the inspector.\n</code></pre>" }, { "textRaw": "`console.profileEnd([label])`", "type": "method", "name": "profileEnd", "meta": { "added": [ "v8.0.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`label` {string}", "name": "label", "type": "string" } ] } ], "desc": "<p>This method does not display anything unless used in the inspector. Stops the\ncurrent JavaScript CPU profiling session if one has been started and prints\nthe report to the <strong>Profiles</strong> panel of the inspector. See\n<a href=\"#consoleprofilelabel\"><code>console.profile()</code></a> for an example.</p>\n<p>If this method is called without a label, the most recently started profile is\nstopped.</p>" }, { "textRaw": "`console.timeStamp([label])`", "type": "method", "name": "timeStamp", "meta": { "added": [ "v8.0.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`label` {string}", "name": "label", "type": "string" } ] } ], "desc": "<p>This method does not display anything unless used in the inspector. The\n<code>console.timeStamp()</code> method adds an event with the label <code>'label'</code> to the\n<strong>Timeline</strong> panel of the inspector.</p>" } ], "type": "module", "displayName": "Inspector only methods" } ], "type": "module", "displayName": "Console" } ] }