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                 <a href="vm.json">View as JSON</a>
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           <div id="toc">
             <h2>Table of Contents</h2>
             <ul>
 <li><a href="#vm_executing_javascript">Executing JavaScript</a><ul>
 <li><a href="#vm_caveats">Caveats</a><ul>
 <li><a href="#vm_sandboxes">Sandboxes</a></li>
 <li><a href="#vm_globals">Globals</a></li>
 </ul>
 </li>
 <li><a href="#vm_vm_runinthiscontext_code_filename">vm.runInThisContext(code, [filename])</a></li>
 <li><a href="#vm_vm_runinnewcontext_code_sandbox_filename">vm.runInNewContext(code, [sandbox], [filename])</a></li>
 <li><a href="#vm_vm_runincontext_code_context_filename">vm.runInContext(code, context, [filename])</a></li>
 <li><a href="#vm_vm_createcontext_initsandbox">vm.createContext([initSandbox])</a></li>
 <li><a href="#vm_vm_createscript_code_filename">vm.createScript(code, [filename])</a></li>
 <li><a href="#vm_class_script">Class: Script</a><ul>
 <li><a href="#vm_script_runinthiscontext">script.runInThisContext()</a></li>
 <li><a href="#vm_script_runinnewcontext_sandbox">script.runInNewContext([sandbox])</a></li>
 </ul>
 </li>
 </ul>
 </li>
 </ul>

           </div>

           <div id="apicontent">
             <h1>Executing JavaScript<span><a class="mark" href="#vm_executing_javascript" id="vm_executing_javascript">#</a></span></h1>
 <pre class="api_stability_2">Stability: 2 - Unstable. See Caveats, below.</pre><!--name=vm-->

 <p>You can access this module with:

 </p>
 <pre><code>var vm = require(&#39;vm&#39;);</code></pre>
 <p>JavaScript code can be compiled and run immediately or compiled, saved, and run later.

 </p>
 <h2>Caveats<span><a class="mark" href="#vm_caveats" id="vm_caveats">#</a></span></h2>
 <p>The <code>vm</code> module has many known issues and edge cases. If you run into
 issues or unexpected behavior, please consult <a href="https://github.com/joyent/node/issues?labels=vm&amp;state=open">the open issues on
 GitHub</a>.
 Some of the biggest problems are described below.

 </p>
 <h3>Sandboxes<span><a class="mark" href="#vm_sandboxes" id="vm_sandboxes">#</a></span></h3>
 <p>The <code>sandbox</code> argument to <code>vm.runInNewContext</code> and <code>vm.createContext</code>,
 along with the <code>initSandbox</code> argument to <code>vm.createContext</code>, do not
 behave as one might normally expect and their behavior varies
 between different versions of Node.

 </p>
 <p>The key issue to be aware of is that V8 provides no way to directly
 control the global object used within a context. As a result, while
 properties of your <code>sandbox</code> object will be available in the context,
 any properties from the <code>prototype</code>s of the <code>sandbox</code> may not be
 available. Furthermore, the <code>this</code> expression within the global scope
 of the context evaluates to the empty object (<code>{}</code>) instead of to
 your sandbox.

 </p>
 <p>Your sandbox&#39;s properties are also not shared directly with the script.
 Instead, the properties of the sandbox are copied into the context at
 the beginning of execution, and then after execution, the properties
 are copied back out in an attempt to propagate any changes.

 </p>
 <h3>Globals<span><a class="mark" href="#vm_globals" id="vm_globals">#</a></span></h3>
 <p>Properties of the global object, like <code>Array</code> and <code>String</code>, have
 different values inside of a context. This means that common
 expressions like <code>[] instanceof Array</code> or
 <code>Object.getPrototypeOf([]) === Array.prototype</code> may not produce
 expected results when used inside of scripts evaluated via the <code>vm</code> module.

 </p>
 <p>Some of these problems have known workarounds listed in the issues for
 <code>vm</code> on GitHub. for example, <code>Array.isArray</code> works around
 the example problem with <code>Array</code>.

 </p>
 <h2>vm.runInThisContext(code, [filename])<span><a class="mark" href="#vm_vm_runinthiscontext_code_filename" id="vm_vm_runinthiscontext_code_filename">#</a></span></h2>
 <p><code>vm.runInThisContext()</code> compiles <code>code</code>, runs it and returns the result. Running
 code does not have access to local scope. <code>filename</code> is optional, it&#39;s used only
 in stack traces.

 </p>
 <p>Example of using <code>vm.runInThisContext</code> and <code>eval</code> to run the same code:

 </p>
 <pre><code>var localVar = 123,
     usingscript, evaled,
     vm = require(&#39;vm&#39;);

 usingscript = vm.runInThisContext(&#39;localVar = 1;&#39;,
   &#39;myfile.vm&#39;);
 console.log(&#39;localVar: &#39; + localVar + &#39;, usingscript: &#39; +
   usingscript);
 evaled = eval(&#39;localVar = 1;&#39;);
 console.log(&#39;localVar: &#39; + localVar + &#39;, evaled: &#39; +
   evaled);

 // localVar: 123, usingscript: 1
 // localVar: 1, evaled: 1</code></pre>
 <p><code>vm.runInThisContext</code> does not have access to the local scope, so <code>localVar</code> is unchanged.
 <code>eval</code> does have access to the local scope, so <code>localVar</code> is changed.

 </p>
 <p>In case of syntax error in <code>code</code>, <code>vm.runInThisContext</code> emits the syntax error to stderr
 and throws an exception.


 </p>
 <h2>vm.runInNewContext(code, [sandbox], [filename])<span><a class="mark" href="#vm_vm_runinnewcontext_code_sandbox_filename" id="vm_vm_runinnewcontext_code_sandbox_filename">#</a></span></h2>
 <p><code>vm.runInNewContext</code> compiles <code>code</code>, then runs it in <code>sandbox</code> and returns the
 result. Running code does not have access to local scope. The object <code>sandbox</code>
 will be used as the global object for <code>code</code>.
 <code>sandbox</code> and <code>filename</code> are optional, <code>filename</code> is only used in stack traces.

 </p>
 <p>Example: compile and execute code that increments a global variable and sets a new one.
 These globals are contained in the sandbox.

 </p>
 <pre><code>var util = require(&#39;util&#39;),
     vm = require(&#39;vm&#39;),
     sandbox = {
       animal: &#39;cat&#39;,
       count: 2
     };

 vm.runInNewContext(&#39;count += 1; name = &quot;kitty&quot;&#39;, sandbox, &#39;myfile.vm&#39;);
 console.log(util.inspect(sandbox));

 // { animal: &#39;cat&#39;, count: 3, name: &#39;kitty&#39; }</code></pre>
 <p>Note that running untrusted code is a tricky business requiring great care.  To prevent accidental
 global variable leakage, <code>vm.runInNewContext</code> is quite useful, but safely running untrusted code
 requires a separate process.

 </p>
 <p>In case of syntax error in <code>code</code>, <code>vm.runInNewContext</code> emits the syntax error to stderr
 and throws an exception.

 </p>
 <h2>vm.runInContext(code, context, [filename])<span><a class="mark" href="#vm_vm_runincontext_code_context_filename" id="vm_vm_runincontext_code_context_filename">#</a></span></h2>
 <p><code>vm.runInContext</code> compiles <code>code</code>, then runs it in <code>context</code> and returns the
 result. A (V8) context comprises a global object, together with a set of
 built-in objects and functions. Running code does not have access to local scope
 and the global object held within <code>context</code> will be used as the global object
 for <code>code</code>.
 <code>filename</code> is optional, it&#39;s used only in stack traces.

 </p>
 <p>Example: compile and execute code in a existing context.

 </p>
 <pre><code>var util = require(&#39;util&#39;),
     vm = require(&#39;vm&#39;),
     initSandbox = {
       animal: &#39;cat&#39;,
       count: 2
     },
     context = vm.createContext(initSandbox);

 vm.runInContext(&#39;count += 1; name = &quot;CATT&quot;&#39;, context, &#39;myfile.vm&#39;);
 console.log(util.inspect(context));

 // { animal: &#39;cat&#39;, count: 3, name: &#39;CATT&#39; }</code></pre>
 <p>Note that <code>createContext</code> will perform a shallow clone of the supplied sandbox object in order to
 initialize the global object of the freshly constructed context.

 </p>
 <p>Note that running untrusted code is a tricky business requiring great care.  To prevent accidental
 global variable leakage, <code>vm.runInContext</code> is quite useful, but safely running untrusted code
 requires a separate process.

 </p>
 <p>In case of syntax error in <code>code</code>, <code>vm.runInContext</code> emits the syntax error to stderr
 and throws an exception.

 </p>
 <h2>vm.createContext([initSandbox])<span><a class="mark" href="#vm_vm_createcontext_initsandbox" id="vm_vm_createcontext_initsandbox">#</a></span></h2>
 <p><code>vm.createContext</code> creates a new context which is suitable for use as the 2nd argument of a subsequent
 call to <code>vm.runInContext</code>. A (V8) context comprises a global object together with a set of
 build-in objects and functions. The optional argument <code>initSandbox</code> will be shallow-copied
 to seed the initial contents of the global object used by the context.

 </p>
 <h2>vm.createScript(code, [filename])<span><a class="mark" href="#vm_vm_createscript_code_filename" id="vm_vm_createscript_code_filename">#</a></span></h2>
 <p><code>createScript</code> compiles <code>code</code> but does not run it. Instead, it returns a
 <code>vm.Script</code> object representing this compiled code. This script can be run
 later many times using methods below. The returned script is not bound to any
 global object. It is bound before each run, just for that run. <code>filename</code> is
 optional, it&#39;s only used in stack traces.

 </p>
 <p>In case of syntax error in <code>code</code>, <code>createScript</code> prints the syntax error to stderr
 and throws an exception.


 </p>
 <h2>Class: Script<span><a class="mark" href="#vm_class_script" id="vm_class_script">#</a></span></h2>
 <p>A class for running scripts.  Returned by vm.createScript.

 </p>
 <h3>script.runInThisContext()<span><a class="mark" href="#vm_script_runinthiscontext" id="vm_script_runinthiscontext">#</a></span></h3>
 <p>Similar to <code>vm.runInThisContext</code> but a method of a precompiled <code>Script</code> object.
 <code>script.runInThisContext</code> runs the code of <code>script</code> and returns the result.
 Running code does not have access to local scope, but does have access to the <code>global</code> object
 (v8: in actual context).

 </p>
 <p>Example of using <code>script.runInThisContext</code> to compile code once and run it multiple times:

 </p>
 <pre><code>var vm = require(&#39;vm&#39;);

 globalVar = 0;

 var script = vm.createScript(&#39;globalVar += 1&#39;, &#39;myfile.vm&#39;);

 for (var i = 0; i &lt; 1000 ; i += 1) {
   script.runInThisContext();
 }

 console.log(globalVar);

 // 1000</code></pre>
 <h3>script.runInNewContext([sandbox])<span><a class="mark" href="#vm_script_runinnewcontext_sandbox" id="vm_script_runinnewcontext_sandbox">#</a></span></h3>
 <p>Similar to <code>vm.runInNewContext</code> a method of a precompiled <code>Script</code> object.
 <code>script.runInNewContext</code> runs the code of <code>script</code> with <code>sandbox</code> as the global object and returns the result.
 Running code does not have access to local scope. <code>sandbox</code> is optional.

 </p>
 <p>Example: compile code that increments a global variable and sets one, then execute this code multiple times.
 These globals are contained in the sandbox.

 </p>
 <pre><code>var util = require(&#39;util&#39;),
     vm = require(&#39;vm&#39;),
     sandbox = {
       animal: &#39;cat&#39;,
       count: 2
     };

 var script = vm.createScript(&#39;count += 1; name = &quot;kitty&quot;&#39;, &#39;myfile.vm&#39;);

 for (var i = 0; i &lt; 10 ; i += 1) {
   script.runInNewContext(sandbox);
 }

 console.log(util.inspect(sandbox));

 // { animal: &#39;cat&#39;, count: 12, name: &#39;kitty&#39; }</code></pre>
 <p>Note that running untrusted code is a tricky business requiring great care.  To prevent accidental
 global variable leakage, <code>script.runInNewContext</code> is quite useful, but safely running untrusted code
 requires a separate process.
 </p>

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	<h1>Node.js v0.10.24 Manual & Documentation</h1>
	<div id="gtoc">
	<p>
	<a href="index.html" name="toc">Index</a> \|
	<a href="all.html">View on single page</a> \|
	<a href="vm.json">View as JSON</a>
	</p>
	</div>
	<hr>
	</header>

	<div id="toc">
	<h2>Table of Contents</h2>
	<ul>
	<li><a href="#vm_executing_javascript">Executing JavaScript</a><ul>
	<li><a href="#vm_caveats">Caveats</a><ul>
	<li><a href="#vm_sandboxes">Sandboxes</a></li>
	<li><a href="#vm_globals">Globals</a></li>
	</ul>
	</li>
	<li><a href="#vm_vm_runinthiscontext_code_filename">vm.runInThisContext(code, [filename])</a></li>
	<li><a href="#vm_vm_runinnewcontext_code_sandbox_filename">vm.runInNewContext(code, [sandbox], [filename])</a></li>
	<li><a href="#vm_vm_runincontext_code_context_filename">vm.runInContext(code, context, [filename])</a></li>
	<li><a href="#vm_vm_createcontext_initsandbox">vm.createContext([initSandbox])</a></li>
	<li><a href="#vm_vm_createscript_code_filename">vm.createScript(code, [filename])</a></li>
	<li><a href="#vm_class_script">Class: Script</a><ul>
	<li><a href="#vm_script_runinthiscontext">script.runInThisContext()</a></li>
	<li><a href="#vm_script_runinnewcontext_sandbox">script.runInNewContext([sandbox])</a></li>
	</ul>
	</li>
	</ul>
	</li>
	</ul>

	</div>

	<div id="apicontent">
	<h1>Executing JavaScript<span><a class="mark" href="#vm_executing_javascript" id="vm_executing_javascript">#</a></span></h1>
	<pre class="api_stability_2">Stability: 2 - Unstable. See Caveats, below.</pre><!--name=vm-->

	<p>You can access this module with:

	</p>
	<pre><code>var vm = require('vm');</code></pre>
	<p>JavaScript code can be compiled and run immediately or compiled, saved, and run later.

	</p>
	<h2>Caveats<span><a class="mark" href="#vm_caveats" id="vm_caveats">#</a></span></h2>
	<p>The <code>vm</code> module has many known issues and edge cases. If you run into
	issues or unexpected behavior, please consult <a href="https://github.com/joyent/node/issues?labels=vm&state=open">the open issues on
	GitHub</a>.
	Some of the biggest problems are described below.

	</p>
	<h3>Sandboxes<span><a class="mark" href="#vm_sandboxes" id="vm_sandboxes">#</a></span></h3>
	<p>The <code>sandbox</code> argument to <code>vm.runInNewContext</code> and <code>vm.createContext</code>,
	along with the <code>initSandbox</code> argument to <code>vm.createContext</code>, do not
	behave as one might normally expect and their behavior varies
	between different versions of Node.

	</p>
	<p>The key issue to be aware of is that V8 provides no way to directly
	control the global object used within a context. As a result, while
	properties of your <code>sandbox</code> object will be available in the context,
	any properties from the <code>prototype</code>s of the <code>sandbox</code> may not be
	available. Furthermore, the <code>this</code> expression within the global scope
	of the context evaluates to the empty object (<code>{}</code>) instead of to
	your sandbox.

	</p>
	<p>Your sandbox's properties are also not shared directly with the script.
	Instead, the properties of the sandbox are copied into the context at
	the beginning of execution, and then after execution, the properties
	are copied back out in an attempt to propagate any changes.

	</p>
	<h3>Globals<span><a class="mark" href="#vm_globals" id="vm_globals">#</a></span></h3>
	<p>Properties of the global object, like <code>Array</code> and <code>String</code>, have
	different values inside of a context. This means that common
	expressions like <code>[] instanceof Array</code> or
	<code>Object.getPrototypeOf([]) === Array.prototype</code> may not produce
	expected results when used inside of scripts evaluated via the <code>vm</code> module.

	</p>
	<p>Some of these problems have known workarounds listed in the issues for
	<code>vm</code> on GitHub. for example, <code>Array.isArray</code> works around
	the example problem with <code>Array</code>.

	</p>
	<h2>vm.runInThisContext(code, [filename])<span><a class="mark" href="#vm_vm_runinthiscontext_code_filename" id="vm_vm_runinthiscontext_code_filename">#</a></span></h2>
	<p><code>vm.runInThisContext()</code> compiles <code>code</code>, runs it and returns the result. Running
	code does not have access to local scope. <code>filename</code> is optional, it's used only
	in stack traces.

	</p>
	<p>Example of using <code>vm.runInThisContext</code> and <code>eval</code> to run the same code:

	</p>
	<pre><code>var localVar = 123,
	usingscript, evaled,
	vm = require('vm');

	usingscript = vm.runInThisContext('localVar = 1;',
	'myfile.vm');
	console.log('localVar: ' + localVar + ', usingscript: ' +
	usingscript);
	evaled = eval('localVar = 1;');
	console.log('localVar: ' + localVar + ', evaled: ' +
	evaled);

	// localVar: 123, usingscript: 1
	// localVar: 1, evaled: 1</code></pre>
	<p><code>vm.runInThisContext</code> does not have access to the local scope, so <code>localVar</code> is unchanged.
	<code>eval</code> does have access to the local scope, so <code>localVar</code> is changed.

	</p>
	<p>In case of syntax error in <code>code</code>, <code>vm.runInThisContext</code> emits the syntax error to stderr
	and throws an exception.


	</p>
	<h2>vm.runInNewContext(code, [sandbox], [filename])<span><a class="mark" href="#vm_vm_runinnewcontext_code_sandbox_filename" id="vm_vm_runinnewcontext_code_sandbox_filename">#</a></span></h2>
	<p><code>vm.runInNewContext</code> compiles <code>code</code>, then runs it in <code>sandbox</code> and returns the
	result. Running code does not have access to local scope. The object <code>sandbox</code>
	will be used as the global object for <code>code</code>.
	<code>sandbox</code> and <code>filename</code> are optional, <code>filename</code> is only used in stack traces.

	</p>
	<p>Example: compile and execute code that increments a global variable and sets a new one.
	These globals are contained in the sandbox.

	</p>
	<pre><code>var util = require('util'),
	vm = require('vm'),
	sandbox = {
	animal: 'cat',
	count: 2
	};

	vm.runInNewContext('count += 1; name = "kitty"', sandbox, 'myfile.vm');
	console.log(util.inspect(sandbox));

	// { animal: 'cat', count: 3, name: 'kitty' }</code></pre>
	<p>Note that running untrusted code is a tricky business requiring great care. To prevent accidental
	global variable leakage, <code>vm.runInNewContext</code> is quite useful, but safely running untrusted code
	requires a separate process.

	</p>
	<p>In case of syntax error in <code>code</code>, <code>vm.runInNewContext</code> emits the syntax error to stderr
	and throws an exception.

	</p>
	<h2>vm.runInContext(code, context, [filename])<span><a class="mark" href="#vm_vm_runincontext_code_context_filename" id="vm_vm_runincontext_code_context_filename">#</a></span></h2>
	<p><code>vm.runInContext</code> compiles <code>code</code>, then runs it in <code>context</code> and returns the
	result. A (V8) context comprises a global object, together with a set of
	built-in objects and functions. Running code does not have access to local scope
	and the global object held within <code>context</code> will be used as the global object
	for <code>code</code>.
	<code>filename</code> is optional, it's used only in stack traces.

	</p>
	<p>Example: compile and execute code in a existing context.

	</p>
	<pre><code>var util = require('util'),
	vm = require('vm'),
	initSandbox = {
	animal: 'cat',
	count: 2
	},
	context = vm.createContext(initSandbox);

	vm.runInContext('count += 1; name = "CATT"', context, 'myfile.vm');
	console.log(util.inspect(context));

	// { animal: 'cat', count: 3, name: 'CATT' }</code></pre>
	<p>Note that <code>createContext</code> will perform a shallow clone of the supplied sandbox object in order to
	initialize the global object of the freshly constructed context.

	</p>
	<p>Note that running untrusted code is a tricky business requiring great care. To prevent accidental
	global variable leakage, <code>vm.runInContext</code> is quite useful, but safely running untrusted code
	requires a separate process.

	</p>
	<p>In case of syntax error in <code>code</code>, <code>vm.runInContext</code> emits the syntax error to stderr
	and throws an exception.

	</p>
	<h2>vm.createContext([initSandbox])<span><a class="mark" href="#vm_vm_createcontext_initsandbox" id="vm_vm_createcontext_initsandbox">#</a></span></h2>
	<p><code>vm.createContext</code> creates a new context which is suitable for use as the 2nd argument of a subsequent
	call to <code>vm.runInContext</code>. A (V8) context comprises a global object together with a set of
	build-in objects and functions. The optional argument <code>initSandbox</code> will be shallow-copied
	to seed the initial contents of the global object used by the context.

	</p>
	<h2>vm.createScript(code, [filename])<span><a class="mark" href="#vm_vm_createscript_code_filename" id="vm_vm_createscript_code_filename">#</a></span></h2>
	<p><code>createScript</code> compiles <code>code</code> but does not run it. Instead, it returns a
	<code>vm.Script</code> object representing this compiled code. This script can be run
	later many times using methods below. The returned script is not bound to any
	global object. It is bound before each run, just for that run. <code>filename</code> is
	optional, it's only used in stack traces.

	</p>
	<p>In case of syntax error in <code>code</code>, <code>createScript</code> prints the syntax error to stderr
	and throws an exception.


	</p>
	<h2>Class: Script<span><a class="mark" href="#vm_class_script" id="vm_class_script">#</a></span></h2>
	<p>A class for running scripts. Returned by vm.createScript.

	</p>
	<h3>script.runInThisContext()<span><a class="mark" href="#vm_script_runinthiscontext" id="vm_script_runinthiscontext">#</a></span></h3>
	<p>Similar to <code>vm.runInThisContext</code> but a method of a precompiled <code>Script</code> object.
	<code>script.runInThisContext</code> runs the code of <code>script</code> and returns the result.
	Running code does not have access to local scope, but does have access to the <code>global</code> object
	(v8: in actual context).

	</p>
	<p>Example of using <code>script.runInThisContext</code> to compile code once and run it multiple times:

	</p>
	<pre><code>var vm = require('vm');

	globalVar = 0;

	var script = vm.createScript('globalVar += 1', 'myfile.vm');

	for (var i = 0; i < 1000 ; i += 1) {
	script.runInThisContext();
	}

	console.log(globalVar);

	// 1000</code></pre>
	<h3>script.runInNewContext([sandbox])<span><a class="mark" href="#vm_script_runinnewcontext_sandbox" id="vm_script_runinnewcontext_sandbox">#</a></span></h3>
	<p>Similar to <code>vm.runInNewContext</code> a method of a precompiled <code>Script</code> object.
	<code>script.runInNewContext</code> runs the code of <code>script</code> with <code>sandbox</code> as the global object and returns the result.
	Running code does not have access to local scope. <code>sandbox</code> is optional.

	</p>
	<p>Example: compile code that increments a global variable and sets one, then execute this code multiple times.
	These globals are contained in the sandbox.

	</p>
	<pre><code>var util = require('util'),
	vm = require('vm'),
	sandbox = {
	animal: 'cat',
	count: 2
	};

	var script = vm.createScript('count += 1; name = "kitty"', 'myfile.vm');

	for (var i = 0; i < 10 ; i += 1) {
	script.runInNewContext(sandbox);
	}

	console.log(util.inspect(sandbox));

	// { animal: 'cat', count: 12, name: 'kitty' }</code></pre>
	<p>Note that running untrusted code is a tricky business requiring great care. To prevent accidental
	global variable leakage, <code>script.runInNewContext</code> is quite useful, but safely running untrusted code
	requires a separate process.
	</p>

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