Revision 707001 of Expression closures

<div class="warning">
 <strong>Non-standard. Do not use!</strong><br />
 The expression closure syntax is a deprecated SpiderMonkey-specific feature and <a href="https://bugzilla.mozilla.org/show_bug.cgi?id=1083458">will be removed</a>. For future-facing usages, consider using <a href="/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions">arrow functions</a>.</div>
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 <div>
  {{jsSidebar("Operators")}}</div>
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<h2 id="Summary">Summary</h2>
<p>Expression closures are a shorthand function syntax for writing simple functions.</p>
<h2 id="Syntax" name="Syntax">Syntax</h2>
<pre class="syntaxbox">
function [<em>name</em>]([<em>param1</em>[, <em>param2[</em>, ..., <em>paramN</em>]]])
   <em>expression</em>
</pre>
<h3 id="Parameters" name="Parameters">Parameters</h3>
<dl>
 <dt>
  <code>name</code></dt>
 <dd>
  The function name. Can be omitted, in which case the function is <em>anonymous</em>. The name is only local to the function body.</dd>
 <dt>
  <code>paramN</code></dt>
 <dd>
  The name of an argument to be passed to the function. A function can have up to 255 arguments.</dd>
 <dt>
  <code>expression</code></dt>
 <dd>
  The expression which comprise the body of the function.</dd>
</dl>
<h2 id="Description" name="Description">Description</h2>
<p>This addition is nothing more than a shorthand for writing simple functions, giving the language something similar to a typical <a class="external" href="https://en.wikipedia.org/wiki/Lambda_calculus#Lambda_calculus_and_programming_languages">Lambda notation</a>.</p>
<p>JavaScript 1.7 and older:</p>
<pre class="brush: js">
function(x) { return x * x; }</pre>
<p>JavaScript 1.8:</p>
<pre class="brush: js">
function(x) x * x</pre>
<p>This syntax allows you to leave off the braces and 'return' statement - making them implicit. There is no added benefit to writing code in this manner, other than having it be syntactically shorter.</p>
<h2 id="Examples" name="Examples">Examples</h2>
<p>A shorthand for binding event listeners:</p>
<pre class="brush: js">
 document.addEventListener("click", function() false, true);
</pre>
<p>Using this notation with some of the array functions from JavaScript 1.6:</p>
<pre class="brush: js">
elems.some(function(elem) elem.type == "text");
</pre>
<h2 id="Browser_compatibility">Browser compatibility</h2>
<p>{{CompatibilityTable}}</p>
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 <table class="compat-table">
  <tbody>
   <tr>
    <th>Feature</th>
    <th>Chrome</th>
    <th>Firefox (Gecko)</th>
    <th>Internet Explorer</th>
    <th>Opera</th>
    <th>Safari</th>
   </tr>
   <tr>
    <td>Basic support</td>
    <td>{{CompatNo}}</td>
    <td>{{CompatVersionUnknown}}</td>
    <td>{{CompatNo}}</td>
    <td>{{CompatNo}}</td>
    <td>{{CompatNo}}</td>
   </tr>
  </tbody>
 </table>
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<div id="compat-mobile">
 <table class="compat-table">
  <tbody>
   <tr>
    <th>Feature</th>
    <th>Android</th>
    <th>Chrome for Android</th>
    <th>Firefox Mobile (Gecko)</th>
    <th>IE Mobile</th>
    <th>Opera Mobile</th>
    <th>Safari Mobile</th>
   </tr>
   <tr>
    <td>Basic support</td>
    <td>{{CompatNo}}</td>
    <td>{{CompatNo}}</td>
    <td>{{CompatVersionUnknown}}</td>
    <td>{{CompatNo}}</td>
    <td>{{CompatNo}}</td>
    <td>{{CompatNo}}</td>
   </tr>
  </tbody>
 </table>
</div>
<h2 id="See_also" name="See_also">See also</h2>
<ul>
 <li>{{jsxref("Functions_and_function_scope", "Functions and function scope")}}</li>
 <li>{{jsxref("Function")}}</li>
 <li>{{jsxref("Statements/function", "function statement")}}</li>
 <li>{{jsxref("Operators/function", "function expression")}}</li>
 <li>{{jsxref("Statements/function*", "function* statement")}}</li>
 <li>{{jsxref("Operators/function*", "function* expression")}}</li>
 <li>{{jsxref("GeneratorFunction")}}</li>
</ul>