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<h1>Node.js v0.10.25 Manual & Documentation</h1>
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<h2>Table of Contents</h2>
<ul>
<li><a href="#util_util">util</a><ul>
<li><a href="#util_util_format_format">util.format(format, [...])</a></li>
<li><a href="#util_util_debug_string">util.debug(string)</a></li>
<li><a href="#util_util_error">util.error([...])</a></li>
<li><a href="#util_util_puts">util.puts([...])</a></li>
<li><a href="#util_util_print">util.print([...])</a></li>
<li><a href="#util_util_log_string">util.log(string)</a></li>
<li><a href="#util_util_inspect_object_options">util.inspect(object, [options])</a><ul>
<li><a href="#util_customizing_util_inspect_colors">Customizing <code>util.inspect</code> colors</a></li>
</ul>
</li>
<li><a href="#util_util_isarray_object">util.isArray(object)</a></li>
<li><a href="#util_util_isregexp_object">util.isRegExp(object)</a></li>
<li><a href="#util_util_isdate_object">util.isDate(object)</a></li>
<li><a href="#util_util_iserror_object">util.isError(object)</a></li>
<li><a href="#util_util_pump_readablestream_writablestream_callback">util.pump(readableStream, writableStream, [callback])</a></li>
<li><a href="#util_util_inherits_constructor_superconstructor">util.inherits(constructor, superConstructor)</a></li>
</ul>
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<div id="apicontent">
<h1>util<span><a class="mark" href="#util_util" id="util_util">#</a></span></h1>
<pre class="api_stability_4">Stability: 4 - API Frozen</pre><p>These functions are in the module <code>'util'</code>. Use <code>require('util')</code> to access
them.
</p>
<h2>util.format(format, [...])<span><a class="mark" href="#util_util_format_format" id="util_util_format_format">#</a></span></h2>
<p>Returns a formatted string using the first argument as a <code>printf</code>-like format.
</p>
<p>The first argument is a string that contains zero or more <em>placeholders</em>.
Each placeholder is replaced with the converted value from its corresponding
argument. Supported placeholders are:
</p>
<ul>
<li><code>%s</code> - String.</li>
<li><code>%d</code> - Number (both integer and float).</li>
<li><code>%j</code> - JSON.</li>
<li><code>%</code> - single percent sign (<code>'%'</code>). This does not consume an argument.</li>
</ul>
<p>If the placeholder does not have a corresponding argument, the placeholder is
not replaced.
</p>
<pre><code>util.format('%s:%s', 'foo'); // 'foo:%s'</code></pre>
<p>If there are more arguments than placeholders, the extra arguments are
converted to strings with <code>util.inspect()</code> and these strings are concatenated,
delimited by a space.
</p>
<pre><code>util.format('%s:%s', 'foo', 'bar', 'baz'); // 'foo:bar baz'</code></pre>
<p>If the first argument is not a format string then <code>util.format()</code> returns
a string that is the concatenation of all its arguments separated by spaces.
Each argument is converted to a string with <code>util.inspect()</code>.
</p>
<pre><code>util.format(1, 2, 3); // '1 2 3'</code></pre>
<h2>util.debug(string)<span><a class="mark" href="#util_util_debug_string" id="util_util_debug_string">#</a></span></h2>
<p>A synchronous output function. Will block the process and
output <code>string</code> immediately to <code>stderr</code>.
</p>
<pre><code>require('util').debug('message on stderr');</code></pre>
<h2>util.error([...])<span><a class="mark" href="#util_util_error" id="util_util_error">#</a></span></h2>
<p>Same as <code>util.debug()</code> except this will output all arguments immediately to
<code>stderr</code>.
</p>
<h2>util.puts([...])<span><a class="mark" href="#util_util_puts" id="util_util_puts">#</a></span></h2>
<p>A synchronous output function. Will block the process and output all arguments
to <code>stdout</code> with newlines after each argument.
</p>
<h2>util.print([...])<span><a class="mark" href="#util_util_print" id="util_util_print">#</a></span></h2>
<p>A synchronous output function. Will block the process, cast each argument to a
string then output to <code>stdout</code>. Does not place newlines after each argument.
</p>
<h2>util.log(string)<span><a class="mark" href="#util_util_log_string" id="util_util_log_string">#</a></span></h2>
<p>Output with timestamp on <code>stdout</code>.
</p>
<pre><code>require('util').log('Timestamped message.');</code></pre>
<h2>util.inspect(object, [options])<span><a class="mark" href="#util_util_inspect_object_options" id="util_util_inspect_object_options">#</a></span></h2>
<p>Return a string representation of <code>object</code>, which is useful for debugging.
</p>
<p>An optional <em>options</em> object may be passed that alters certain aspects of the
formatted string:
</p>
<ul>
<li><p><code>showHidden</code> - if <code>true</code> then the object's non-enumerable properties will be
shown too. Defaults to <code>false</code>.</p>
</li>
<li><p><code>depth</code> - tells <code>inspect</code> how many times to recurse while formatting the
object. This is useful for inspecting large complicated objects. Defaults to
<code>2</code>. To make it recurse indefinitely pass <code>null</code>.</p>
</li>
<li><p><code>colors</code> - if <code>true</code>, then the output will be styled with ANSI color codes.
Defaults to <code>false</code>. Colors are customizable, see below.</p>
</li>
<li><p><code>customInspect</code> - if <code>false</code>, then custom <code>inspect()</code> functions defined on the
objects being inspected won't be called. Defaults to <code>true</code>.</p>
</li>
</ul>
<p>Example of inspecting all properties of the <code>util</code> object:
</p>
<pre><code>var util = require('util');
console.log(util.inspect(util, { showHidden: true, depth: null }));</code></pre>
<h3>Customizing <code>util.inspect</code> colors<span><a class="mark" href="#util_customizing_util_inspect_colors" id="util_customizing_util_inspect_colors">#</a></span></h3>
<p>Color output (if enabled) of <code>util.inspect</code> is customizable globally
via <code>util.inspect.styles</code> and <code>util.inspect.colors</code> objects.
</p>
<p><code>util.inspect.styles</code> is a map assigning each style a color
from <code>util.inspect.colors</code>.
Highlighted styles and their default values are:
<em> <code>number</code> (yellow)
</em> <code>boolean</code> (yellow)
<em> <code>string</code> (green)
</em> <code>date</code> (magenta)
<em> <code>regexp</code> (red)
</em> <code>null</code> (bold)
<em> <code>undefined</code> (grey)
</em> <code>special</code> - only function at this time (cyan)
* <code>name</code> (intentionally no styling)
</p>
<p>Predefined color codes are: <code>white</code>, <code>grey</code>, <code>black</code>, <code>blue</code>, <code>cyan</code>,
<code>green</code>, <code>magenta</code>, <code>red</code> and <code>yellow</code>.
There are also <code>bold</code>, <code>italic</code>, <code>underline</code> and <code>inverse</code> codes.
</p>
<p>Objects also may define their own <code>inspect(depth)</code> function which <code>util.inspect()</code>
will invoke and use the result of when inspecting the object:
</p>
<pre><code>var util = require('util');
var obj = { name: 'nate' };
obj.inspect = function(depth) {
return '{' + this.name + '}';
};
util.inspect(obj);
// "{nate}"</code></pre>
<h2>util.isArray(object)<span><a class="mark" href="#util_util_isarray_object" id="util_util_isarray_object">#</a></span></h2>
<p>Returns <code>true</code> if the given "object" is an <code>Array</code>. <code>false</code> otherwise.
</p>
<pre><code>var util = require('util');
util.isArray([])
// true
util.isArray(new Array)
// true
util.isArray({})
// false</code></pre>
<h2>util.isRegExp(object)<span><a class="mark" href="#util_util_isregexp_object" id="util_util_isregexp_object">#</a></span></h2>
<p>Returns <code>true</code> if the given "object" is a <code>RegExp</code>. <code>false</code> otherwise.
</p>
<pre><code>var util = require('util');
util.isRegExp(/some regexp/)
// true
util.isRegExp(new RegExp('another regexp'))
// true
util.isRegExp({})
// false</code></pre>
<h2>util.isDate(object)<span><a class="mark" href="#util_util_isdate_object" id="util_util_isdate_object">#</a></span></h2>
<p>Returns <code>true</code> if the given "object" is a <code>Date</code>. <code>false</code> otherwise.
</p>
<pre><code>var util = require('util');
util.isDate(new Date())
// true
util.isDate(Date())
// false (without 'new' returns a String)
util.isDate({})
// false</code></pre>
<h2>util.isError(object)<span><a class="mark" href="#util_util_iserror_object" id="util_util_iserror_object">#</a></span></h2>
<p>Returns <code>true</code> if the given "object" is an <code>Error</code>. <code>false</code> otherwise.
</p>
<pre><code>var util = require('util');
util.isError(new Error())
// true
util.isError(new TypeError())
// true
util.isError({ name: 'Error', message: 'an error occurred' })
// false</code></pre>
<h2>util.pump(readableStream, writableStream, [callback])<span><a class="mark" href="#util_util_pump_readablestream_writablestream_callback" id="util_util_pump_readablestream_writablestream_callback">#</a></span></h2>
<pre class="api_stability_0">Stability: 0 - Deprecated: Use readableStream.pipe(writableStream)</pre><p>Read the data from <code>readableStream</code> and send it to the <code>writableStream</code>.
When <code>writableStream.write(data)</code> returns <code>false</code> <code>readableStream</code> will be
paused until the <code>drain</code> event occurs on the <code>writableStream</code>. <code>callback</code> gets
an error as its only argument and is called when <code>writableStream</code> is closed or
when an error occurs.
</p>
<h2>util.inherits(constructor, superConstructor)<span><a class="mark" href="#util_util_inherits_constructor_superconstructor" id="util_util_inherits_constructor_superconstructor">#</a></span></h2>
<p>Inherit the prototype methods from one
<a href="https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Object/constructor">constructor</a>
into another. The prototype of <code>constructor</code> will be set to a new
object created from <code>superConstructor</code>.
</p>
<p>As an additional convenience, <code>superConstructor</code> will be accessible
through the <code>constructor.super_</code> property.
</p>
<pre><code>var util = require("util");
var events = require("events");
function MyStream() {
events.EventEmitter.call(this);
}
util.inherits(MyStream, events.EventEmitter);
MyStream.prototype.write = function(data) {
this.emit("data", data);
}
var stream = new MyStream();
console.log(stream instanceof events.EventEmitter); // true
console.log(MyStream.super_ === events.EventEmitter); // true
stream.on("data", function(data) {
console.log('Received data: "' + data + '"');
})
stream.write("It works!"); // Received data: "It works!"</code></pre>
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