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make the new faster isEmpty a little safer too
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@jashkenas
jashkenas committed Feb 24, 2010
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<meta http-equiv="content-type" content="text/html;charset=UTF-8" />
<meta http-equiv="X-UA-Compatible" content="chrome=1">
<title>Underscore.js</title>
<script src="underscore.js"></script>
<style>
body {
font-size: 16px;
Expand Down Expand Up @@ -89,7 +88,7 @@ <h1>Underscore.js</h1>
as well as more specialized helpers: function binding, javascript
templating, deep equality testing, and so on. It delegates to built-in
functions, if present, so modern browsers will use the
native implementations of <b>forEach</b>, <b>map</b>, <b>reduce</b>,
native implementations of <b>forEach</b>, <b>map</b>, <b>reduce</b>,
<b>filter</b>, <b>every</b>, <b>some</b> and <b>indexOf</b>.
</p>

Expand All @@ -102,7 +101,7 @@ <h1>Underscore.js</h1>
The unabridged source code is
<a href="http://github.com/documentcloud/underscore/">available on GitHub</a>.
</p>

<p>
<i>Underscore is an open-source component of <a href="http://documentcloud.org/">DocumentCloud</a>.</i>
</p>
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=&gt; {lumberjack : 2, all : 4, night : 2 ... }</pre>

<p>
In addition, the
<a href="https://developer.mozilla.org/En/Core_JavaScript_1.5_Reference/Objects/Array">Array prototype's methods</a>
are proxied through the chained Underscore object, so you can slip a
<tt>reverse</tt> or a <tt>push</tt> into your chain, and continue to
In addition, the
<a href="https://developer.mozilla.org/En/Core_JavaScript_1.5_Reference/Objects/Array">Array prototype's methods</a>
are proxied through the chained Underscore object, so you can slip a
<tt>reverse</tt> or a <tt>push</tt> into your chain, and continue to
modify the array.
</p>

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<a href="#isEqual">isEqual</a>, <a href="#isEmpty">isEmpty</a>, <a href="#isElement">isElement</a>,
<a href="#isArray">isArray</a>, <a href="#isArguments">isArguments</a>, <a href="#isFunction">isFunction</a>, <a href="#isString">isString</a>,
<a href="#isNumber">isNumber</a>, <a href="#isDate">isDate</a>, <a href="#isRegExp">isRegExp</a>
<a href="#isNaN">isNaN</a>, <a href="#isNull">isNull</a>,
<a href="#isNaN">isNaN</a>, <a href="#isNull">isNull</a>,
<a href="#isUndefined">isUndefined</a>
</span>
</p>
Expand Down Expand Up @@ -240,7 +239,7 @@ <h2>Collection Functions (Arrays or Objects)</h2>
function. The <b>iterator</b> is bound to the <b>context</b> object, if one is
passed. Each invocation of <b>iterator</b> is called with three arguments:
<tt>(element, index, list)</tt>. If <b>list</b> is a JavaScript object, <b>iterator</b>'s
arguments will be <tt>(value, key, list)</tt>. Use <a href="#breakLoop"><tt>breakLoop</tt></a>
arguments will be <tt>(value, key, list)</tt>. Use <a href="#breakLoop"><tt>breakLoop</tt></a>
to break out of the iteration. Delegates to the native
<b>forEach</b> function if it exists.
</p>
Expand Down Expand Up @@ -461,7 +460,7 @@ <h2>Collection Functions (Arrays or Objects)</h2>
</pre>

<h2>Array Functions</h2>

<p>
<i>Note: All array functions will also work on the <b>arguments</b> object.</i>
</p>
Expand All @@ -470,7 +469,7 @@ <h2>Array Functions</h2>
<b class="header">first</b><code>_.first(array, [n])</code>
<span class="alias">Alias: <b>head</b></span>
<br />
Returns the first element of an <b>array</b>. Passing <b>n</b> will
Returns the first element of an <b>array</b>. Passing <b>n</b> will
return the first <b>n</b> elements of the array.
</p>
<pre>
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<span class="alias">Alias: <b>methods</b></span>
<br />
Returns a sorted list of the names of every method in an object &mdash;
that is to say, the name of every function property of the object.
that is to say, the name of every function property of the object.
</p>
<pre>
_.functions(_);
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<p id="tap">
<b class="header">tap</b><code>_.tap(object, interceptor)</code>
<br />
Invokes <b>interceptor</b> with the <b>object</b>, and then returns <b>object</b>.
Invokes <b>interceptor</b> with the <b>object</b>, and then returns <b>object</b>.
The primary purpose of this method is to "tap into" a method chain, in order to perform operations on intermediate results within the chain.
</p>
<pre>
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<b class="header">breakLoop</b><code>_.breakLoop()</code>
<br />
Breaks out of the current loop iteration. Similar to the <tt>break</tt>
keyword in regular "for" loop, but works within an iterator function.
keyword in regular "for" loop, but works within an iterator function.
Uses the native <tt>StopIteration</tt> object in JavaScript 1.7 compliant
browsers.
</p>
<pre>
var result = null;
_.each([1, 2, 3], function(num) {
if ((result = num) == 2) _.breakLoop();
_.each([1, 2, 3], function(num) {
if ((result = num) == 2) _.breakLoop();
});
result;
=&gt; 2</pre>
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template settings to use different symbols to set off interpolated code.
Define <b>start</b> and <b>end</b> tokens, and an <b>interpolate</b> regex
to match expressions that should be evaluated and inserted. For example,
to perform
<a href="http://github.com/janl/mustache.js#readme">Mustache.js</a>
to perform
<a href="http://github.com/janl/mustache.js#readme">Mustache.js</a>
style templating:
</p>

<pre>
_.templateSettings = {
start : '{{',
end : '}}',
interpolate : /\{\{(.+?)\}\}/g
};

var template = _.template("Hello {{ name }}!");
template({name : "Mustache"});
=&gt; "Hello Mustache!"</pre>
Expand Down Expand Up @@ -1055,168 +1054,168 @@ <h2>Chaining</h2>
</pre>

<h2 id="duck_typing">Duck Typing</h2>

<p>
The <b>isType</b> (<tt>isArray</tt>, <tt>isFunction</tt>, <tt>isString</tt> ...) family of type-checking
functions use property detection to do their work, which, although
orders of magnitude faster than the alternative, isn't entirely safe when dealing
with objects that are used as hashes, where arbitrary strings are being
set for the keys. It's entirely possible for an object to masquerade as
another type, if you're setting properties with names like "concat" and
orders of magnitude faster than the alternative, isn't entirely safe when dealing
with objects that are used as hashes, where arbitrary strings are being
set for the keys. It's entirely possible for an object to masquerade as
another type, if you're setting properties with names like "concat" and
"charCodeAt". So be aware.
</p>


<h2>Links &amp; Suggested Reading</h2>

<p>
<a href="http://mirven.github.com/underscore.lua/">Underscore.lua</a>,
a Lua port of the functions that are applicable in both languages.
a Lua port of the functions that are applicable in both languages.
Includes OOP-wrapping and chaining.
The <a href="http://github.com/mirven/underscore.lua">source</a> is
The <a href="http://github.com/mirven/underscore.lua">source</a> is
available on GitHub.
</p>

<p>
Ruby's <a href="http://ruby-doc.org/core/classes/Enumerable.html">Enumerable</a> module.
</p>

<p>
<a href="http://www.prototypejs.org/">Prototype.js</a>, which provides
JavaScript with collection functions in the manner closest to Ruby's Enumerable.
</p>

<p>
Oliver Steele's
Oliver Steele's
<a href="http://osteele.com/sources/javascript/functional/">Functional JavaScript</a>,
which includes comprehensive higher-order function support as well as string lambdas.
</p>

<p>
Python's <a href="http://docs.python.org/library/itertools.html">itertools</a>.
</p>

<h2>Change Log</h2>

<p>
<b class="header">0.5.8</b><br />
Fixed Underscore's collection functions to work on
<a href="https://developer.mozilla.org/En/DOM/NodeList">NodeLists</a> and
Fixed Underscore's collection functions to work on
<a href="https://developer.mozilla.org/En/DOM/NodeList">NodeLists</a> and
<a href="https://developer.mozilla.org/En/DOM/HTMLCollection">HTMLCollections</a>
once more, thanks to
once more, thanks to
<a href="http://github.com/jmtulloss">Justin Tulloss</a>.
</p>

<p>
<b class="header">0.5.7</b><br />
A safer implementation of <tt>_.isArguments</tt>, and a
faster <tt>_.isNumber</tt>,<br />thanks to
A safer implementation of <tt>_.isArguments</tt>, and a
faster <tt>_.isNumber</tt>,<br />thanks to
<a href="http://jedschmidt.com/">Jed Schmidt</a>.
</p>

<p>
<b class="header">0.5.6</b><br />
Customizable delimiters for <tt>_.template</tt>, contributed by
<a href="http://github.com/iamnoah">Noah Sloan</a>.
</p>

<p>
<b class="header">0.5.5</b><br />
Fix for a bug in MobileSafari's OOP-wrapper, with the arguments object.
</p>

<p>
<b class="header">0.5.4</b><br />
Fix for multiple single quotes within a template string for
<tt>_.template</tt>. See:
Fix for multiple single quotes within a template string for
<tt>_.template</tt>. See:
<a href="http://www.west-wind.com/Weblog/posts/509108.aspx">Rick Strahl's blog post</a>.
</p>

<p>
<b class="header">0.5.2</b><br />
New implementations of <tt>isArray</tt>, <tt>isDate</tt>, <tt>isFunction</tt>,
<tt>isNumber</tt>, <tt>isRegExp</tt>, and <tt>isString</tt>, thanks to
a suggestion from
<a href="http://www.broofa.com/">Robert Kieffer</a>.
New implementations of <tt>isArray</tt>, <tt>isDate</tt>, <tt>isFunction</tt>,
<tt>isNumber</tt>, <tt>isRegExp</tt>, and <tt>isString</tt>, thanks to
a suggestion from
<a href="http://www.broofa.com/">Robert Kieffer</a>.
Instead of doing <tt>Object#toString</tt>
comparisons, they now check for expected properties, which is less safe,
but more than an order of magnitude faster. Most other Underscore
functions saw minor speed improvements as a result.
comparisons, they now check for expected properties, which is less safe,
but more than an order of magnitude faster. Most other Underscore
functions saw minor speed improvements as a result.
<a href="http://dolzhenko.org/">Evgeniy Dolzhenko</a>
contributed <tt>_.tap</tt>,
<a href="http://ruby-doc.org/core-1.9/classes/Object.html#M000191">similar to Ruby 1.9's</a>,
contributed <tt>_.tap</tt>,
<a href="http://ruby-doc.org/core-1.9/classes/Object.html#M000191">similar to Ruby 1.9's</a>,
which is handy for injecting side effects (like logging) into chained calls.
</p>

<p>
<b class="header">0.5.1</b><br />
Added an <tt>_.isArguments</tt> function. Lots of little safety checks
and optimizations contributed by
and optimizations contributed by
<a href="http://github.com/iamnoah/">Noah Sloan</a> and Andri Möll.
</p>

<p>
<b class="header">0.5.0</b><br />
<b>[API Changes]</b> <tt>_.bindAll</tt> now takes the context object as
its first parameter. If no method names are passed, all of the context
<b>[API Changes]</b> <tt>_.bindAll</tt> now takes the context object as
its first parameter. If no method names are passed, all of the context
object's methods are bound to it, enabling chaining and easier binding.
<tt>_.functions</tt> now takes a single argument and returns the names
<tt>_.functions</tt> now takes a single argument and returns the names
of its Function properties. Calling <tt>_.functions(_)</tt> will get you
the previous behavior.
Added <tt>_.isRegExp</tt> so that <tt>isEqual</tt> can now test for RegExp equality.
All of the "is" functions have been shrunk down into a single definition.
<a href="http://github.com/grayrest/">Karl Guertin</a> contributed patches.
</p>

<p>
<b class="header">0.4.7</b><br />
Added <tt>isDate</tt>, <tt>isNaN</tt>, and <tt>isNull</tt>, for completeness.
Optimizations for <tt>isEqual</tt> when checking equality between Arrays
or Dates. <tt>_.keys</tt> is now <small><i><b>25%&ndash;2X</b></i></small> faster (depending on your
browser) which speeds up the functions that rely on it, such as <tt>_.each</tt>.
</p>

<p>
<b class="header">0.4.6</b><br />
Added the <tt>range</tt> function, a port of the
<a href="http://docs.python.org/library/functions.html#range">Python
Added the <tt>range</tt> function, a port of the
<a href="http://docs.python.org/library/functions.html#range">Python
function of the same name</a>, for generating flexibly-numbered lists
of integers. Original patch contributed by
of integers. Original patch contributed by
<a href="http://github.com/kylichuku">Kirill Ishanov</a>.
</p>

<p>
<b class="header">0.4.5</b><br />
Added <tt>rest</tt> for Arrays and arguments objects, and aliased
Added <tt>rest</tt> for Arrays and arguments objects, and aliased
<tt>first</tt> as <tt>head</tt>, and <tt>rest</tt> as <tt>tail</tt>,
thanks to <a href="http://github.com/lukesutton/">Luke Sutton</a>'s patches.
Added tests ensuring that all Underscore Array functions also work on
<i>arguments</i> objects.
</p>

<p>
<b class="header">0.4.4</b><br />
Added <tt>isString</tt>, and <tt>isNumber</tt>, for consistency. Fixed
<tt>_.isEqual(NaN, NaN)</tt> to return <i>true</i> (which is debatable).
<tt>_.isEqual(NaN, NaN)</tt> to return <i>true</i> (which is debatable).
</p>

<p>
<b class="header">0.4.3</b><br />
Started using the native <tt>StopIteration</tt> object in browsers that support it.
Fixed Underscore setup for CommonJS environments.
</p>

<p>
<b class="header">0.4.2</b><br />
Renamed the unwrapping function to <tt>value</tt>, for clarity.
</p>

<p>
<b class="header">0.4.1</b><br />
Chained Underscore objects now support the Array prototype methods, so
that you can perform the full range of operations on a wrapped array
without having to break your chain. Added a <tt>breakLoop</tt> method
to <b>break</b> in the middle of any Underscore iteration. Added an
to <b>break</b> in the middle of any Underscore iteration. Added an
<tt>isEmpty</tt> function that works on arrays and objects.
</p>

Expand Down Expand Up @@ -1288,5 +1287,8 @@ <h2>Change Log</h2>

</div>

<!-- Include Underscore, so you can play with it in the console. -->
<script type="text/javascript" src="underscore.js"></script>

</body>
</html>
3 changes: 2 additions & 1 deletion test/objects.js
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Expand Up @@ -60,6 +60,7 @@ $(document).ready(function() {
ok(_.isEmpty([]), '[] is empty');
ok(!_.isEmpty({one : 1}), '{one : 1} is not empty');
ok(_.isEmpty({}), '{} is empty');
ok(_.isEmpty(new RegExp('')), 'objects with prototype properties are empty');
ok(_.isEmpty(null), 'null is empty');
ok(_.isEmpty(), 'undefined is empty');

Expand Down Expand Up @@ -102,7 +103,7 @@ $(document).ready(function() {
ok(_.isArguments(args), 'but the arguments object is an arguments object');
ok(!_.isArguments(_.toArray(args)), 'but not when it\'s converted into an array');
ok(!_.isArguments([1,2,3]), 'and not vanilla arrays.');
ok(_.isArguments(iArguments), 'event from another frame');
ok(_.isArguments(iArguments), 'even from another frame');
});

test("objects: isArray", function() {
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