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<!doctype html> <html lang="en"> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width"> <meta name="nodejs.org:node-version" content="v12.20.0"> <title>Console | Node.js v12.20.0 Documentation</title> <link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Lato:400,700,400italic&display=fallback"> <link rel="stylesheet" href="assets/style.css"> <link rel="stylesheet" href="assets/hljs.css"> <link rel="canonical" href="https://nodejs.org/api/console.html"> </head> <body class="alt apidoc" id="api-section-console"> <div id="content" class="clearfix"> <div id="column2" class="interior"> <div id="intro" class="interior"> <a href="/" title="Go back to the home page"> Node.js </a> </div> <ul> <li><a href="documentation.html" class="nav-documentation">About this documentation</a></li> <li><a href="synopsis.html" class="nav-synopsis">Usage and example</a></li> </ul> <hr class="line"> <ul> <li><a href="assert.html" class="nav-assert">Assertion testing</a></li> <li><a href="async_hooks.html" class="nav-async_hooks">Async hooks</a></li> <li><a href="buffer.html" class="nav-buffer">Buffer</a></li> <li><a href="addons.html" class="nav-addons">C++ Addons</a></li> <li><a href="n-api.html" class="nav-n-api">C/C++ Addons with N-API</a></li> <li><a href="embedding.html" class="nav-embedding">C++ Embedder API</a></li> <li><a href="child_process.html" class="nav-child_process">Child Processes</a></li> <li><a href="cluster.html" class="nav-cluster">Cluster</a></li> <li><a href="cli.html" class="nav-cli">Command line options</a></li> <li><a href="console.html" class="nav-console active">Console</a></li> <li><a href="crypto.html" class="nav-crypto">Crypto</a></li> <li><a href="debugger.html" class="nav-debugger">Debugger</a></li> <li><a href="deprecations.html" class="nav-deprecations">Deprecated APIs</a></li> <li><a href="dns.html" class="nav-dns">DNS</a></li> <li><a href="domain.html" class="nav-domain">Domain</a></li> <li><a href="errors.html" class="nav-errors">Errors</a></li> <li><a href="events.html" class="nav-events">Events</a></li> <li><a href="fs.html" class="nav-fs">File system</a></li> <li><a href="globals.html" class="nav-globals">Globals</a></li> <li><a href="http.html" class="nav-http">HTTP</a></li> <li><a href="http2.html" class="nav-http2">HTTP/2</a></li> <li><a href="https.html" class="nav-https">HTTPS</a></li> <li><a href="inspector.html" class="nav-inspector">Inspector</a></li> <li><a href="intl.html" class="nav-intl">Internationalization</a></li> <li><a href="modules.html" class="nav-modules">Modules: CommonJS modules</a></li> <li><a href="esm.html" class="nav-esm">Modules: ECMAScript modules</a></li> <li><a href="module.html" class="nav-module">Modules: <code>module</code> API</a></li> <li><a href="packages.html" class="nav-packages">Modules: Packages</a></li> <li><a href="net.html" class="nav-net">Net</a></li> <li><a href="os.html" class="nav-os">OS</a></li> <li><a href="path.html" class="nav-path">Path</a></li> <li><a href="perf_hooks.html" class="nav-perf_hooks">Performance hooks</a></li> <li><a href="policy.html" class="nav-policy">Policies</a></li> <li><a href="process.html" class="nav-process">Process</a></li> <li><a href="punycode.html" class="nav-punycode">Punycode</a></li> <li><a href="querystring.html" class="nav-querystring">Query strings</a></li> <li><a href="readline.html" class="nav-readline">Readline</a></li> <li><a href="repl.html" class="nav-repl">REPL</a></li> <li><a href="report.html" class="nav-report">Report</a></li> <li><a href="stream.html" class="nav-stream">Stream</a></li> <li><a href="string_decoder.html" class="nav-string_decoder">String decoder</a></li> <li><a href="timers.html" class="nav-timers">Timers</a></li> <li><a href="tls.html" class="nav-tls">TLS/SSL</a></li> <li><a href="tracing.html" class="nav-tracing">Trace events</a></li> <li><a href="tty.html" class="nav-tty">TTY</a></li> <li><a href="dgram.html" class="nav-dgram">UDP/datagram</a></li> <li><a href="url.html" class="nav-url">URL</a></li> <li><a href="util.html" class="nav-util">Utilities</a></li> <li><a href="v8.html" class="nav-v8">V8</a></li> <li><a href="vm.html" class="nav-vm">VM</a></li> <li><a href="wasi.html" class="nav-wasi">WASI</a></li> <li><a href="worker_threads.html" class="nav-worker_threads">Worker threads</a></li> <li><a href="zlib.html" class="nav-zlib">Zlib</a></li> </ul> <hr class="line"> <ul> <li><a href="https://github.com/nodejs/node" class="nav-https-github-com-nodejs-node">Code repository and issue tracker</a></li> </ul> </div> <div id="column1" data-id="console" class="interior"> <header> <h1>Node.js v12.20.0 Documentation</h1> <div id="gtoc"> <ul> <li> <a href="index.html">Index</a> </li> <li> <a href="all.html">View on single page</a> </li> <li> <a href="console.json">View as JSON</a> </li> <li class="version-picker"> <a href="#">View another version <span>▼</span></a> <ol class="version-picker"><li><a href="https://nodejs.org/docs/latest-v15.x/api/console.html">15.x</a></li> <li><a href="https://nodejs.org/docs/latest-v14.x/api/console.html">14.x <b>LTS</b></a></li> <li><a href="https://nodejs.org/docs/latest-v13.x/api/console.html">13.x</a></li> <li><a href="https://nodejs.org/docs/latest-v12.x/api/console.html">12.x <b>LTS</b></a></li> <li><a href="https://nodejs.org/docs/latest-v11.x/api/console.html">11.x</a></li> <li><a href="https://nodejs.org/docs/latest-v10.x/api/console.html">10.x <b>LTS</b></a></li> <li><a href="https://nodejs.org/docs/latest-v9.x/api/console.html">9.x</a></li> <li><a href="https://nodejs.org/docs/latest-v8.x/api/console.html">8.x</a></li> <li><a href="https://nodejs.org/docs/latest-v7.x/api/console.html">7.x</a></li> <li><a href="https://nodejs.org/docs/latest-v6.x/api/console.html">6.x</a></li> <li><a href="https://nodejs.org/docs/latest-v5.x/api/console.html">5.x</a></li> <li><a href="https://nodejs.org/docs/latest-v4.x/api/console.html">4.x</a></li> <li><a href="https://nodejs.org/docs/latest-v0.12.x/api/console.html">0.12.x</a></li> <li><a href="https://nodejs.org/docs/latest-v0.10.x/api/console.html">0.10.x</a></li></ol> </li> <li class="edit_on_github"><a href="https://github.com/nodejs/node/edit/master/doc/api/console.md"><span class="github_icon"><svg height="16" width="16" viewBox="0 0 16.1 16.1" fill="currentColor"><path d="M8 0a8 8 0 0 0-2.5 15.6c.4 0 .5-.2.5-.4v-1.5c-2 .4-2.5-.5-2.7-1 0-.1-.5-.9-.8-1-.3-.2-.7-.6 0-.6.6 0 1 .6 1.2.8.7 1.2 1.9 1 2.4.7 0-.5.2-.9.5-1-1.8-.3-3.7-1-3.7-4 0-.9.3-1.6.8-2.2 0-.2-.3-1 .1-2 0 0 .7-.3 2.2.7a7.4 7.4 0 0 1 4 0c1.5-1 2.2-.8 2.2-.8.5 1.1.2 2 .1 2.1.5.6.8 1.3.8 2.2 0 3-1.9 3.7-3.6 4 .3.2.5.7.5 1.4v2.2c0 .2.1.5.5.4A8 8 0 0 0 16 8a8 8 0 0 0-8-8z"/></svg></span>Edit on GitHub</a></li> </ul> </div> <hr> </header> <div id="toc"> <h2>Table of Contents</h2> <ul> <li><span class="stability_2"><a href="#console_console">Console</a></span> <ul> <li><a href="#console_class_console">Class: <code>Console</code></a> <ul> <li><a href="#console_new_console_stdout_stderr_ignoreerrors"><code>new Console(stdout[, stderr][, ignoreErrors])</code></a></li> <li><a href="#console_new_console_options"><code>new Console(options)</code></a></li> <li><a href="#console_console_assert_value_message"><code>console.assert(value[, ...message])</code></a></li> <li><a href="#console_console_clear"><code>console.clear()</code></a></li> <li><a href="#console_console_count_label"><code>console.count([label])</code></a></li> <li><a href="#console_console_countreset_label"><code>console.countReset([label])</code></a></li> <li><a href="#console_console_debug_data_args"><code>console.debug(data[, ...args])</code></a></li> <li><a href="#console_console_dir_obj_options"><code>console.dir(obj[, options])</code></a></li> <li><a href="#console_console_dirxml_data"><code>console.dirxml(...data)</code></a></li> <li><a href="#console_console_error_data_args"><code>console.error([data][, ...args])</code></a></li> <li><a href="#console_console_group_label"><code>console.group([...label])</code></a></li> <li><a href="#console_console_groupcollapsed"><code>console.groupCollapsed()</code></a></li> <li><a href="#console_console_groupend"><code>console.groupEnd()</code></a></li> <li><a href="#console_console_info_data_args"><code>console.info([data][, ...args])</code></a></li> <li><a href="#console_console_log_data_args"><code>console.log([data][, ...args])</code></a></li> <li><a href="#console_console_table_tabulardata_properties"><code>console.table(tabularData[, properties])</code></a></li> <li><a href="#console_console_time_label"><code>console.time([label])</code></a></li> <li><a href="#console_console_timeend_label"><code>console.timeEnd([label])</code></a></li> <li><a href="#console_console_timelog_label_data"><code>console.timeLog([label][, ...data])</code></a></li> <li><a href="#console_console_trace_message_args"><code>console.trace([message][, ...args])</code></a></li> <li><a href="#console_console_warn_data_args"><code>console.warn([data][, ...args])</code></a></li> </ul> </li> <li><a href="#console_inspector_only_methods">Inspector only methods</a> <ul> <li><a href="#console_console_profile_label"><code>console.profile([label])</code></a></li> <li><a href="#console_console_profileend_label"><code>console.profileEnd([label])</code></a></li> <li><a href="#console_console_timestamp_label"><code>console.timeStamp([label])</code></a></li> </ul> </li> </ul> </li> </ul> </div> <div id="apicontent"> <h1>Console<span><a class="mark" href="#console_console" id="console_console">#</a></span></h1> <p></p><div class="api_stability api_stability_2"><a href="documentation.html#documentation_stability_index">Stability: 2</a> - Stable</div><p></p> <p><strong>Source Code:</strong> <a href="https://github.com/nodejs/node/blob/v12.20.0/lib/console.js">lib/console.js</a></p> <p>The <code>console</code> module provides a simple debugging console that is similar to the JavaScript console mechanism provided by web browsers.</p> <p>The module exports two specific components:</p> <ul> <li>A <code>Console</code> class with methods such as <code>console.log()</code>, <code>console.error()</code> and <code>console.warn()</code> that can be used to write to any Node.js stream.</li> <li>A global <code>console</code> instance configured to write to <a href="process.html#process_process_stdout"><code>process.stdout</code></a> and <a href="process.html#process_process_stderr"><code>process.stderr</code></a>. The global <code>console</code> can be used without calling <code>require('console')</code>.</li> </ul> <p><strong><em>Warning</em></strong>: 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 <a href="process.html#process_a_note_on_process_i_o">note on process I/O</a> for more information.</p> <p>Example using the global <code>console</code>:</p> <pre><code class="language-js"><span class="hljs-built_in">console</span>.log(<span class="hljs-string">'hello world'</span>); <span class="hljs-comment">// Prints: hello world, to stdout</span> <span class="hljs-built_in">console</span>.log(<span class="hljs-string">'hello %s'</span>, <span class="hljs-string">'world'</span>); <span class="hljs-comment">// Prints: hello world, to stdout</span> <span class="hljs-built_in">console</span>.error(<span class="hljs-keyword">new</span> <span class="hljs-built_in">Error</span>(<span class="hljs-string">'Whoops, something bad happened'</span>)); <span class="hljs-comment">// Prints: [Error: Whoops, something bad happened], to stderr</span> <span class="hljs-keyword">const</span> name = <span class="hljs-string">'Will Robinson'</span>; <span class="hljs-built_in">console</span>.warn(<span class="hljs-string">`Danger <span class="hljs-subst">${name}</span>! Danger!`</span>); <span class="hljs-comment">// Prints: Danger Will Robinson! Danger!, to stderr</span></code></pre> <p>Example using the <code>Console</code> class:</p> <pre><code class="language-js"><span class="hljs-keyword">const</span> out = getStreamSomehow(); <span class="hljs-keyword">const</span> err = getStreamSomehow(); <span class="hljs-keyword">const</span> myConsole = <span class="hljs-keyword">new</span> <span class="hljs-built_in">console</span>.Console(out, err); myConsole.log(<span class="hljs-string">'hello world'</span>); <span class="hljs-comment">// Prints: hello world, to out</span> myConsole.log(<span class="hljs-string">'hello %s'</span>, <span class="hljs-string">'world'</span>); <span class="hljs-comment">// Prints: hello world, to out</span> myConsole.error(<span class="hljs-keyword">new</span> <span class="hljs-built_in">Error</span>(<span class="hljs-string">'Whoops, something bad happened'</span>)); <span class="hljs-comment">// Prints: [Error: Whoops, something bad happened], to err</span> <span class="hljs-keyword">const</span> name = <span class="hljs-string">'Will Robinson'</span>; myConsole.warn(<span class="hljs-string">`Danger <span class="hljs-subst">${name}</span>! Danger!`</span>); <span class="hljs-comment">// Prints: Danger Will Robinson! Danger!, to err</span></code></pre> <h2>Class: <code>Console</code><span><a class="mark" href="#console_class_console" id="console_class_console">#</a></span></h2> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tbody><tr><th>Version</th><th>Changes</th></tr> <tr><td>v8.0.0</td> <td><p>Errors that occur while writing to the underlying streams will now be ignored by default.</p></td></tr> </tbody></table> </details> </div> <p>The <code>Console</code> class can be used to create a simple logger with configurable output streams and can be accessed using either <code>require('console').Console</code> or <code>console.Console</code> (or their destructured counterparts):</p> <pre><code class="language-js"><span class="hljs-keyword">const</span> { Console } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'console'</span>);</code></pre> <pre><code class="language-js"><span class="hljs-keyword">const</span> { Console } = <span class="hljs-built_in">console</span>;</code></pre> <h3><code>new Console(stdout[, stderr][, ignoreErrors])</code><span><a class="mark" href="#console_new_console_stdout_stderr_ignoreerrors" id="console_new_console_stdout_stderr_ignoreerrors">#</a></span></h3> <h3><code>new Console(options)</code><span><a class="mark" href="#console_new_console_options" id="console_new_console_options">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tbody><tr><th>Version</th><th>Changes</th></tr> <tr><td>v12.17.0</td> <td><p>The <code>groupIndentation</code> option was introduced.</p></td></tr> <tr><td>v11.7.0</td> <td><p>The <code>inspectOptions</code> option is introduced.</p></td></tr> <tr><td>v10.0.0</td> <td><p>The <code>Console</code> constructor now supports an <code>options</code> argument, and the <code>colorMode</code> option was introduced.</p></td></tr> <tr><td>v8.0.0</td> <td><p>The <code>ignoreErrors</code> option was introduced.</p></td></tr> </tbody></table> </details> </div> <ul> <li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> <ul> <li><code>stdout</code> <a href="stream.html#stream_class_stream_writable" class="type"><stream.Writable></a></li> <li><code>stderr</code> <a href="stream.html#stream_class_stream_writable" class="type"><stream.Writable></a></li> <li><code>ignoreErrors</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Ignore errors when writing to the underlying streams. <strong>Default:</strong> <code>true</code>.</li> <li><code>colorMode</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Set color support for this <code>Console</code> instance. Setting to <code>true</code> enables coloring while inspecting values. Setting to <code>false</code> disables coloring while inspecting values. Setting to <code>'auto'</code> makes color support depend on the value of the <code>isTTY</code> property and the value returned by <code>getColorDepth()</code> on the respective stream. This option can not be used, if <code>inspectOptions.colors</code> is set as well. <strong>Default:</strong> <code>'auto'</code>.</li> <li><code>inspectOptions</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Specifies options that are passed along to <a href="util.html#util_util_inspect_object_options"><code>util.inspect()</code></a>.</li> <li><code>groupIndentation</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Set group indentation. <strong>Default:</strong> <code>2</code>.</li> </ul> </li> </ul> <p>Creates a new <code>Console</code> with one or two writable stream instances. <code>stdout</code> is a writable stream to print log or info output. <code>stderr</code> is used for warning or error output. If <code>stderr</code> is not provided, <code>stdout</code> is used for <code>stderr</code>.</p> <pre><code class="language-js"><span class="hljs-keyword">const</span> output = fs.createWriteStream(<span class="hljs-string">'./stdout.log'</span>); <span class="hljs-keyword">const</span> errorOutput = fs.createWriteStream(<span class="hljs-string">'./stderr.log'</span>); <span class="hljs-comment">// Custom simple logger</span> <span class="hljs-keyword">const</span> logger = <span class="hljs-keyword">new</span> Console({ <span class="hljs-attr">stdout</span>: output, <span class="hljs-attr">stderr</span>: errorOutput }); <span class="hljs-comment">// use it like console</span> <span class="hljs-keyword">const</span> count = <span class="hljs-number">5</span>; logger.log(<span class="hljs-string">'count: %d'</span>, count); <span class="hljs-comment">// In stdout.log: count 5</span></code></pre> <p>The global <code>console</code> is a special <code>Console</code> whose output is sent to <a href="process.html#process_process_stdout"><code>process.stdout</code></a> and <a href="process.html#process_process_stderr"><code>process.stderr</code></a>. It is equivalent to calling:</p> <pre><code class="language-js"><span class="hljs-keyword">new</span> Console({ <span class="hljs-attr">stdout</span>: process.stdout, <span class="hljs-attr">stderr</span>: process.stderr });</code></pre> <h3><code>console.assert(value[, ...message])</code><span><a class="mark" href="#console_console_assert_value_message" id="console_console_assert_value_message">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tbody><tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>The implementation is now spec compliant and does not throw anymore.</p></td></tr> <tr><td>v0.1.101</td> <td><p><span>Added in: v0.1.101</span></p></td></tr> </tbody></table> </details> </div> <ul> <li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> The value tested for being truthy.</li> <li><code>...message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> All arguments besides <code>value</code> are used as error message.</li> </ul> <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 writes a message and does not otherwise affect execution. The output always starts with <code>"Assertion failed"</code>. If provided, <code>message</code> is formatted using <a href="util.html#util_util_format_format_args"><code>util.format()</code></a>.</p> <p>If <code>value</code> is <a href="https://developer.mozilla.org/en-US/docs/Glossary/Truthy">truthy</a>, nothing happens.</p> <pre><code class="language-js"><span class="hljs-built_in">console</span>.assert(<span class="hljs-literal">true</span>, <span class="hljs-string">'does nothing'</span>); <span class="hljs-built_in">console</span>.assert(<span class="hljs-literal">false</span>, <span class="hljs-string">'Whoops %s work'</span>, <span class="hljs-string">'didn\'t'</span>); <span class="hljs-comment">// Assertion failed: Whoops didn't work</span> <span class="hljs-built_in">console</span>.assert(); <span class="hljs-comment">// Assertion failed</span></code></pre> <h3><code>console.clear()</code><span><a class="mark" href="#console_console_clear" id="console_console_clear">#</a></span></h3> <div class="api_metadata"> <span>Added in: v8.3.0</span> </div> <p>When <code>stdout</code> is a TTY, calling <code>console.clear()</code> will attempt to clear the TTY. When <code>stdout</code> is not a TTY, this method does nothing.</p> <p>The specific operation of <code>console.clear()</code> can vary across operating systems and terminal types. For most Linux operating systems, <code>console.clear()</code> operates similarly to the <code>clear</code> shell command. On Windows, <code>console.clear()</code> will clear only the output in the current terminal viewport for the Node.js binary.</p> <h3><code>console.count([label])</code><span><a class="mark" href="#console_console_count_label" id="console_console_count_label">#</a></span></h3> <div class="api_metadata"> <span>Added in: v8.3.0</span> </div> <ul> <li><code>label</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The display label for the counter. <strong>Default:</strong> <code>'default'</code>.</li> </ul> <p>Maintains an internal counter specific to <code>label</code> and outputs to <code>stdout</code> the number of times <code>console.count()</code> has been called with the given <code>label</code>.</p> <!-- eslint-skip --> <pre><code class="language-js">> <span class="hljs-built_in">console</span>.count() <span class="hljs-attr">default</span>: <span class="hljs-number">1</span> <span class="hljs-literal">undefined</span> > <span class="hljs-built_in">console</span>.count(<span class="hljs-string">'default'</span>) <span class="hljs-attr">default</span>: <span class="hljs-number">2</span> <span class="hljs-literal">undefined</span> > <span class="hljs-built_in">console</span>.count(<span class="hljs-string">'abc'</span>) <span class="hljs-attr">abc</span>: <span class="hljs-number">1</span> <span class="hljs-literal">undefined</span> > <span class="hljs-built_in">console</span>.count(<span class="hljs-string">'xyz'</span>) <span class="hljs-attr">xyz</span>: <span class="hljs-number">1</span> <span class="hljs-literal">undefined</span> > <span class="hljs-built_in">console</span>.count(<span class="hljs-string">'abc'</span>) <span class="hljs-attr">abc</span>: <span class="hljs-number">2</span> <span class="hljs-literal">undefined</span> > <span class="hljs-built_in">console</span>.count() <span class="hljs-attr">default</span>: <span class="hljs-number">3</span> <span class="hljs-literal">undefined</span> ></code></pre> <h3><code>console.countReset([label])</code><span><a class="mark" href="#console_console_countreset_label" id="console_console_countreset_label">#</a></span></h3> <div class="api_metadata"> <span>Added in: v8.3.0</span> </div> <ul> <li><code>label</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The display label for the counter. <strong>Default:</strong> <code>'default'</code>.</li> </ul> <p>Resets the internal counter specific to <code>label</code>.</p> <!-- eslint-skip --> <pre><code class="language-js">> <span class="hljs-built_in">console</span>.count(<span class="hljs-string">'abc'</span>); abc: <span class="hljs-number">1</span> <span class="hljs-literal">undefined</span> > <span class="hljs-built_in">console</span>.countReset(<span class="hljs-string">'abc'</span>); <span class="hljs-literal">undefined</span> > <span class="hljs-built_in">console</span>.count(<span class="hljs-string">'abc'</span>); abc: <span class="hljs-number">1</span> <span class="hljs-literal">undefined</span> ></code></pre> <h3><code>console.debug(data[, ...args])</code><span><a class="mark" href="#console_console_debug_data_args" id="console_console_debug_data_args">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tbody><tr><th>Version</th><th>Changes</th></tr> <tr><td>v8.10.0</td> <td><p><code>console.debug</code> is now an alias for <code>console.log</code>.</p></td></tr> <tr><td>v8.0.0</td> <td><p><span>Added in: v8.0.0</span></p></td></tr> </tbody></table> </details> </div> <ul> <li><code>data</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> <li><code>...args</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> </ul> <p>The <code>console.debug()</code> function is an alias for <a href="#console_console_log_data_args"><code>console.log()</code></a>.</p> <h3><code>console.dir(obj[, options])</code><span><a class="mark" href="#console_console_dir_obj_options" id="console_console_dir_obj_options">#</a></span></h3> <div class="api_metadata"> <span>Added in: v0.1.101</span> </div> <ul> <li><code>obj</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> <li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> <ul> <li><code>showHidden</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If <code>true</code> then the object's non-enumerable and symbol properties will be shown too. <strong>Default:</strong> <code>false</code>.</li> <li><code>depth</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Tells <a href="util.html#util_util_inspect_object_options"><code>util.inspect()</code></a> how many times to recurse while formatting the object. This is useful for inspecting large complicated objects. To make it recurse indefinitely, pass <code>null</code>. <strong>Default:</strong> <code>2</code>.</li> <li><code>colors</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If <code>true</code>, then the output will be styled with ANSI color codes. Colors are customizable; see <a href="util.html#util_customizing_util_inspect_colors">customizing <code>util.inspect()</code> colors</a>. <strong>Default:</strong> <code>false</code>.</li> </ul> </li> </ul> <p>Uses <a href="util.html#util_util_inspect_object_options"><code>util.inspect()</code></a> on <code>obj</code> and prints the resulting string to <code>stdout</code>. This function bypasses any custom <code>inspect()</code> function defined on <code>obj</code>.</p> <h3><code>console.dirxml(...data)</code><span><a class="mark" href="#console_console_dirxml_data" id="console_console_dirxml_data">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tbody><tr><th>Version</th><th>Changes</th></tr> <tr><td>v9.3.0</td> <td><p><code>console.dirxml</code> now calls <code>console.log</code> for its arguments.</p></td></tr> <tr><td>v8.0.0</td> <td><p><span>Added in: v8.0.0</span></p></td></tr> </tbody></table> </details> </div> <ul> <li><code>...data</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> </ul> <p>This method calls <code>console.log()</code> passing it the arguments received. This method does not produce any XML formatting.</p> <h3><code>console.error([data][, ...args])</code><span><a class="mark" href="#console_console_error_data_args" id="console_console_error_data_args">#</a></span></h3> <div class="api_metadata"> <span>Added in: v0.1.100</span> </div> <ul> <li><code>data</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> <li><code>...args</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> </ul> <p>Prints to <code>stderr</code> with newline. Multiple arguments can be passed, with the first used as the primary message and all additional used as substitution values 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 <a href="util.html#util_util_format_format_args"><code>util.format()</code></a>).</p> <pre><code class="language-js"><span class="hljs-keyword">const</span> code = <span class="hljs-number">5</span>; <span class="hljs-built_in">console</span>.error(<span class="hljs-string">'error #%d'</span>, code); <span class="hljs-comment">// Prints: error #5, to stderr</span> <span class="hljs-built_in">console</span>.error(<span class="hljs-string">'error'</span>, code); <span class="hljs-comment">// Prints: error 5, to stderr</span></code></pre> <p>If formatting elements (e.g. <code>%d</code>) are not found in the first string then <a href="util.html#util_util_inspect_object_options"><code>util.inspect()</code></a> is called on each argument and the resulting string values are concatenated. See <a href="util.html#util_util_format_format_args"><code>util.format()</code></a> for more information.</p> <h3><code>console.group([...label])</code><span><a class="mark" href="#console_console_group_label" id="console_console_group_label">#</a></span></h3> <div class="api_metadata"> <span>Added in: v8.5.0</span> </div> <ul> <li><code>...label</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> </ul> <p>Increases indentation of subsequent lines by spaces for <code>groupIndentation</code> length.</p> <p>If one or more <code>label</code>s are provided, those are printed first without the additional indentation.</p> <h3><code>console.groupCollapsed()</code><span><a class="mark" href="#console_console_groupcollapsed" id="console_console_groupcollapsed">#</a></span></h3> <div class="api_metadata"> <span>Added in: v8.5.0</span> </div> <p>An alias for <a href="#console_console_group_label"><code>console.group()</code></a>.</p> <h3><code>console.groupEnd()</code><span><a class="mark" href="#console_console_groupend" id="console_console_groupend">#</a></span></h3> <div class="api_metadata"> <span>Added in: v8.5.0</span> </div> <p>Decreases indentation of subsequent lines by spaces for <code>groupIndentation</code> length.</p> <h3><code>console.info([data][, ...args])</code><span><a class="mark" href="#console_console_info_data_args" id="console_console_info_data_args">#</a></span></h3> <div class="api_metadata"> <span>Added in: v0.1.100</span> </div> <ul> <li><code>data</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> <li><code>...args</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> </ul> <p>The <code>console.info()</code> function is an alias for <a href="#console_console_log_data_args"><code>console.log()</code></a>.</p> <h3><code>console.log([data][, ...args])</code><span><a class="mark" href="#console_console_log_data_args" id="console_console_log_data_args">#</a></span></h3> <div class="api_metadata"> <span>Added in: v0.1.100</span> </div> <ul> <li><code>data</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> <li><code>...args</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> </ul> <p>Prints to <code>stdout</code> with newline. Multiple arguments can be passed, with the first used as the primary message and all additional used as substitution values 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 <a href="util.html#util_util_format_format_args"><code>util.format()</code></a>).</p> <pre><code class="language-js"><span class="hljs-keyword">const</span> count = <span class="hljs-number">5</span>; <span class="hljs-built_in">console</span>.log(<span class="hljs-string">'count: %d'</span>, count); <span class="hljs-comment">// Prints: count: 5, to stdout</span> <span class="hljs-built_in">console</span>.log(<span class="hljs-string">'count:'</span>, count); <span class="hljs-comment">// Prints: count: 5, to stdout</span></code></pre> <p>See <a href="util.html#util_util_format_format_args"><code>util.format()</code></a> for more information.</p> <h3><code>console.table(tabularData[, properties])</code><span><a class="mark" href="#console_console_table_tabulardata_properties" id="console_console_table_tabulardata_properties">#</a></span></h3> <div class="api_metadata"> <span>Added in: v10.0.0</span> </div> <ul> <li><code>tabularData</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> <li><code>properties</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a> Alternate properties for constructing the table.</li> </ul> <p>Try to construct a table with the columns of the properties of <code>tabularData</code> (or use <code>properties</code>) and rows of <code>tabularData</code> and log it. Falls back to just logging the argument if it can’t be parsed as tabular.</p> <pre><code class="language-js"><span class="hljs-comment">// These can't be parsed as tabular data</span> <span class="hljs-built_in">console</span>.table(<span class="hljs-built_in">Symbol</span>()); <span class="hljs-comment">// Symbol()</span> <span class="hljs-built_in">console</span>.table(<span class="hljs-literal">undefined</span>); <span class="hljs-comment">// undefined</span> <span class="hljs-built_in">console</span>.table([{ <span class="hljs-attr">a</span>: <span class="hljs-number">1</span>, <span class="hljs-attr">b</span>: <span class="hljs-string">'Y'</span> }, { <span class="hljs-attr">a</span>: <span class="hljs-string">'Z'</span>, <span class="hljs-attr">b</span>: <span class="hljs-number">2</span> }]); <span class="hljs-comment">// ┌─────────┬─────┬─────┐</span> <span class="hljs-comment">// │ (index) │ a │ b │</span> <span class="hljs-comment">// ├─────────┼─────┼─────┤</span> <span class="hljs-comment">// │ 0 │ 1 │ 'Y' │</span> <span class="hljs-comment">// │ 1 │ 'Z' │ 2 │</span> <span class="hljs-comment">// └─────────┴─────┴─────┘</span> <span class="hljs-built_in">console</span>.table([{ <span class="hljs-attr">a</span>: <span class="hljs-number">1</span>, <span class="hljs-attr">b</span>: <span class="hljs-string">'Y'</span> }, { <span class="hljs-attr">a</span>: <span class="hljs-string">'Z'</span>, <span class="hljs-attr">b</span>: <span class="hljs-number">2</span> }], [<span class="hljs-string">'a'</span>]); <span class="hljs-comment">// ┌─────────┬─────┐</span> <span class="hljs-comment">// │ (index) │ a │</span> <span class="hljs-comment">// ├─────────┼─────┤</span> <span class="hljs-comment">// │ 0 │ 1 │</span> <span class="hljs-comment">// │ 1 │ 'Z' │</span> <span class="hljs-comment">// └─────────┴─────┘</span></code></pre> <h3><code>console.time([label])</code><span><a class="mark" href="#console_console_time_label" id="console_console_time_label">#</a></span></h3> <div class="api_metadata"> <span>Added in: v0.1.104</span> </div> <ul> <li><code>label</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> <strong>Default:</strong> <code>'default'</code></li> </ul> <p>Starts a timer that can be used to compute the duration of an operation. Timers are identified by a unique <code>label</code>. Use the same <code>label</code> when calling <a href="#console_console_timeend_label"><code>console.timeEnd()</code></a> to stop the timer and output the elapsed time in milliseconds to <code>stdout</code>. Timer durations are accurate to the sub-millisecond.</p> <h3><code>console.timeEnd([label])</code><span><a class="mark" href="#console_console_timeend_label" id="console_console_timeend_label">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tbody><tr><th>Version</th><th>Changes</th></tr> <tr><td>v6.0.0</td> <td><p>This method no longer supports multiple calls that don’t map to individual <code>console.time()</code> calls; see below for details.</p></td></tr> <tr><td>v0.1.104</td> <td><p><span>Added in: v0.1.104</span></p></td></tr> </tbody></table> </details> </div> <ul> <li><code>label</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> <strong>Default:</strong> <code>'default'</code></li> </ul> <p>Stops a timer that was previously started by calling <a href="#console_console_time_label"><code>console.time()</code></a> and prints the result to <code>stdout</code>:</p> <pre><code class="language-js"><span class="hljs-built_in">console</span>.time(<span class="hljs-string">'100-elements'</span>); <span class="hljs-keyword">for</span> (<span class="hljs-keyword">let</span> i = <span class="hljs-number">0</span>; i < <span class="hljs-number">100</span>; i++) {} <span class="hljs-built_in">console</span>.timeEnd(<span class="hljs-string">'100-elements'</span>); <span class="hljs-comment">// prints 100-elements: 225.438ms</span></code></pre> <h3><code>console.timeLog([label][, ...data])</code><span><a class="mark" href="#console_console_timelog_label_data" id="console_console_timelog_label_data">#</a></span></h3> <div class="api_metadata"> <span>Added in: v10.7.0</span> </div> <ul> <li><code>label</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> <strong>Default:</strong> <code>'default'</code></li> <li><code>...data</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> </ul> <p>For a timer that was previously started by calling <a href="#console_console_time_label"><code>console.time()</code></a>, prints the elapsed time and other <code>data</code> arguments to <code>stdout</code>:</p> <pre><code class="language-js"><span class="hljs-built_in">console</span>.time(<span class="hljs-string">'process'</span>); <span class="hljs-keyword">const</span> value = expensiveProcess1(); <span class="hljs-comment">// Returns 42</span> <span class="hljs-built_in">console</span>.timeLog(<span class="hljs-string">'process'</span>, value); <span class="hljs-comment">// Prints "process: 365.227ms 42".</span> doExpensiveProcess2(value); <span class="hljs-built_in">console</span>.timeEnd(<span class="hljs-string">'process'</span>);</code></pre> <h3><code>console.trace([message][, ...args])</code><span><a class="mark" href="#console_console_trace_message_args" id="console_console_trace_message_args">#</a></span></h3> <div class="api_metadata"> <span>Added in: v0.1.104</span> </div> <ul> <li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> <li><code>...args</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> </ul> <p>Prints to <code>stderr</code> the string <code>'Trace: '</code>, followed by the <a href="util.html#util_util_format_format_args"><code>util.format()</code></a> formatted message and stack trace to the current position in the code.</p> <pre><code class="language-js"><span class="hljs-built_in">console</span>.trace(<span class="hljs-string">'Show me'</span>); <span class="hljs-comment">// Prints: (stack trace will vary based on where trace is called)</span> <span class="hljs-comment">// Trace: Show me</span> <span class="hljs-comment">// at repl:2:9</span> <span class="hljs-comment">// at REPLServer.defaultEval (repl.js:248:27)</span> <span class="hljs-comment">// at bound (domain.js:287:14)</span> <span class="hljs-comment">// at REPLServer.runBound [as eval] (domain.js:300:12)</span> <span class="hljs-comment">// at REPLServer.<anonymous> (repl.js:412:12)</span> <span class="hljs-comment">// at emitOne (events.js:82:20)</span> <span class="hljs-comment">// at REPLServer.emit (events.js:169:7)</span> <span class="hljs-comment">// at REPLServer.Interface._onLine (readline.js:210:10)</span> <span class="hljs-comment">// at REPLServer.Interface._line (readline.js:549:8)</span> <span class="hljs-comment">// at REPLServer.Interface._ttyWrite (readline.js:826:14)</span></code></pre> <h3><code>console.warn([data][, ...args])</code><span><a class="mark" href="#console_console_warn_data_args" id="console_console_warn_data_args">#</a></span></h3> <div class="api_metadata"> <span>Added in: v0.1.100</span> </div> <ul> <li><code>data</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> <li><code>...args</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> </ul> <p>The <code>console.warn()</code> function is an alias for <a href="#console_console_error_data_args"><code>console.error()</code></a>.</p> <h2>Inspector only methods<span><a class="mark" href="#console_inspector_only_methods" id="console_inspector_only_methods">#</a></span></h2> <p>The following methods are exposed by the V8 engine in the general API but do not display anything unless used in conjunction with the <a href="debugger.html">inspector</a> (<code>--inspect</code> flag).</p> <h3><code>console.profile([label])</code><span><a class="mark" href="#console_console_profile_label" id="console_console_profile_label">#</a></span></h3> <div class="api_metadata"> <span>Added in: v8.0.0</span> </div> <ul> <li><code>label</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> </ul> <p>This method does not display anything unless used in the inspector. The <code>console.profile()</code> method starts a JavaScript CPU profile with an optional label until <a href="#console_console_profileend_label"><code>console.profileEnd()</code></a> is called. The profile is then added to the <strong>Profile</strong> panel of the inspector.</p> <pre><code class="language-js"><span class="hljs-built_in">console</span>.profile(<span class="hljs-string">'MyLabel'</span>); <span class="hljs-comment">// Some code</span> <span class="hljs-built_in">console</span>.profileEnd(<span class="hljs-string">'MyLabel'</span>); <span class="hljs-comment">// Adds the profile 'MyLabel' to the Profiles panel of the inspector.</span></code></pre> <h3><code>console.profileEnd([label])</code><span><a class="mark" href="#console_console_profileend_label" id="console_console_profileend_label">#</a></span></h3> <div class="api_metadata"> <span>Added in: v8.0.0</span> </div> <ul> <li><code>label</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> </ul> <p>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 <strong>Profiles</strong> panel of the inspector. See <a href="#console_console_profile_label"><code>console.profile()</code></a> for an example.</p> <p>If this method is called without a label, the most recently started profile is stopped.</p> <h3><code>console.timeStamp([label])</code><span><a class="mark" href="#console_console_timestamp_label" id="console_console_timestamp_label">#</a></span></h3> <div class="api_metadata"> <span>Added in: v8.0.0</span> </div> <ul> <li><code>label</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> </ul> <p>This method does not display anything unless used in the inspector. The <code>console.timeStamp()</code> method adds an event with the label <code>'label'</code> to the <strong>Timeline</strong> panel of the inspector.</p> <!-- API END --> </div> </div> </div> </body> </html>
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