path: root/files/ca/web/javascript/reference/functions/arguments/index.html

---
title: Arguments object
slug: Web/JavaScript/Reference/Functions/arguments
tags:
  - Functions
  - JavaScript
  - NeedsTranslation
  - TopicStub
  - arguments
translation_of: Web/JavaScript/Reference/Functions/arguments
---
<div>
<div>{{jsSidebar("Functions")}}</div>
</div>

<p>The <strong><code>arguments</code></strong> object is an <code>Array</code>-like object corresponding to the arguments passed to a function.</p>

<h2 id="Syntax">Syntax</h2>

<pre class="syntaxbox">arguments</pre>

<h2 id="Description">Description</h2>

<p>The <code>arguments</code> object is a local variable available within all functions. <code>arguments</code> as a property of <code>Function</code> can no longer be used.</p>

<p>You can refer to a function's arguments within the function by using the <code>arguments</code> object. This object contains an entry for each argument passed to the function, the first entry's index starting at 0. For example, if a function is passed three arguments, you can refer to the argument as follows:</p>

<pre class="brush: js">arguments[0]
arguments[1]
arguments[2]
</pre>

<p>The arguments can also be set:</p>

<pre class="brush: js">arguments[1] = 'new value';</pre>

<p>The <code>arguments</code> object is not an {{jsxref("Array")}}. It is similar to an <code>Array</code>, but does not have any <code>Array</code> properties except <code><a href="/en-US/docs/Web/JavaScript/Reference/Functions/arguments/length" title="JavaScript/Reference/Functions_and_function_scope/arguments/length">length</a></code>. For example, it does not have the <code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/pop" title="JavaScript/Reference/Global_Objects/Array/pop">pop</a></code> method. However it can be converted to a real <code>Array</code>:</p>

<pre class="brush: js">var args = Array.prototype.slice.call(arguments);</pre>

<div class="warning">
<p><strong>Important:</strong> You should not slice on arguments because it prevents optimizations in JavaScript engines (V8 for example). Instead, try constructing a new array by iterating through the arguments object. <a href="https://github.com/petkaantonov/bluebird/wiki/Optimization-killers#3-managing-arguments">More information</a>.</p>
</div>

<p>If <a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array#Array_generic_methods" title="https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Array#Array_generic_methods">Array generics</a> are available, one can use the following instead:</p>

<pre class="brush: js">var args = Array.slice(arguments);</pre>

<p>The <code>arguments</code> object is available only within a function body. Attempting to access the <code>arguments</code> object outside a function declaration results in an error.</p>

<p>You can use the <code>arguments</code> object if you call a function with more arguments than it is formally declared to accept. This technique is useful for functions that can be passed a variable number of arguments. You can use <code><a href="/en-US/docs/JavaScript/Reference/Functions_and_function_scope/arguments/length" title="JavaScript/Reference/Functions_and_function_scope/arguments/length">arguments.length</a></code> to determine the number of arguments passed to the function, and then process each argument by using the <code>arguments</code> object. (To determine the number of arguments declared when a function was defined, use the <code><a href="/en-US/docs/JavaScript/Reference/Global_Objects/Function/length" title="JavaScript/Reference/Global_Objects/Function/length">Function.length</a></code> property.)</p>

<h2 id="Properties">Properties</h2>

<dl>
 <dt><code><a href="/en-US/docs/Web/JavaScript/Reference/Functions/arguments/callee" title="JavaScript/Reference/Functions_and_function_scope/arguments/callee">arguments.callee</a></code></dt>
 <dd>Reference to the currently executing function.</dd>
 <dt><code><a href="/en-US/docs/Web/JavaScript/Reference/Functions/arguments/caller" title="JavaScript/Reference/Functions_and_function_scope/arguments/caller">arguments.caller</a></code> {{ Obsolete_inline() }}</dt>
 <dd>Reference to the function that invoked the currently executing function.</dd>
 <dt><code><a href="/en-US/docs/Web/JavaScript/Reference/Functions/arguments/length" title="JavaScript/Reference/Functions_and_function_scope/arguments/length">arguments.length</a></code></dt>
 <dd>Reference to the number of arguments passed to the function.</dd>
</dl>

<h2 id="Examples">Examples</h2>

<h3 id="Defining_a_function_that_concatenates_several_strings">Defining a function that concatenates several strings</h3>

<p>This example defines a function that concatenates several strings. The only formal argument for the function is a string that specifies the characters that separate the items to concatenate. The function is defined as follows:</p>

<pre class="brush:js">function myConcat(separator) {
  var args = Array.prototype.slice.call(arguments, 1);
  return args.join(separator);
}</pre>

<p>You can pass any number of arguments to this function, and it creates a list using each argument as an item in the list.</p>

<pre class="brush:js">// returns "red, orange, blue"
myConcat(", ", "red", "orange", "blue");

// returns "elephant; giraffe; lion; cheetah"
myConcat("; ", "elephant", "giraffe", "lion", "cheetah");

// returns "sage. basil. oregano. pepper. parsley"
myConcat(". ", "sage", "basil", "oregano", "pepper", "parsley");</pre>

<h3 id="Defining_a_function_that_creates_HTML_lists">Defining a function that creates HTML lists</h3>

<p>This example defines a function that creates a string containing HTML for a list. The only formal argument for the function is a string that is "<code>u</code>" if the list is to be unordered (bulleted), or "<code>o</code>" if the list is to be ordered (numbered). The function is defined as follows:</p>

<pre class="brush:js">function list(type) {
  var result = "&lt;" + type + "l&gt;&lt;li&gt;";
  var args = Array.prototype.slice.call(arguments, 1);
  result += args.join("&lt;/li&gt;&lt;li&gt;");
  result += "&lt;/li&gt;&lt;/" + type + "l&gt;"; // end list

  return result;
}</pre>

<p>You can pass any number of arguments to this function, and it adds each argument as an item to a list of the type indicated. For example:</p>

<pre class="brush:js">var listHTML = list("u", "One", "Two", "Three");

/* listHTML is:

"&lt;ul&gt;&lt;li&gt;One&lt;/li&gt;&lt;li&gt;Two&lt;/li&gt;&lt;li&gt;Three&lt;/li&gt;&lt;/ul&gt;"

*/</pre>

<h3 id="Rest_default_and_destructured_parameters">Rest, default and destructured parameters</h3>

<p>The <code>arguments</code> object can be used in conjunction with <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/rest_parameters">rest parameters</a>, <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Default_parameters">default parameters</a> or <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment">destructured parameters</a>.</p>

<pre class="brush: js">function foo(...args) {
  return arguments;
}
foo(1, 2, 3); // { "0": 1, "1": 2, "2": 3 }
</pre>

<p>However, in non-strict functions, a <strong>mapped <code>arguments</code> object</strong> is only provided if the function does <strong>not</strong> contain any <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/rest_parameters">rest parameters</a>, any <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Default_parameters">default parameters</a> or any <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment">destructured parameters</a>. For example, in the following function that uses a default parameter, <code>1</code>0 instead of 100 is returned:</p>

<pre class="brush: js">function bar(a=1) {
  arguments[0] = 100;
  return a;
}
bar(10); // 10
</pre>

<h2 id="Specifications">Specifications</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">Comment</th>
  </tr>
  <tr>
   <td>{{SpecName('ES1')}}</td>
   <td>{{Spec2('ES1')}}</td>
   <td>Initial definition. Implemented in JavaScript 1.1</td>
  </tr>
  <tr>
   <td>{{SpecName('ES5.1', '#sec-10.6', 'Arguments Object')}}</td>
   <td>{{Spec2('ES5.1')}}</td>
   <td> </td>
  </tr>
  <tr>
   <td>{{SpecName('ES6', '#sec-arguments-exotic-objects', 'Arguments Exotic Objects')}}</td>
   <td>{{Spec2('ES6')}}</td>
   <td> </td>
  </tr>
 </tbody>
</table>

<h2 id="Browser_compatibility">Browser compatibility</h2>

<p>{{CompatibilityTable}}</p>

<div id="compat-desktop">
<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>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

<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>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

<h2 id="See_also">See also</h2>

<ul>
 <li>{{jsxref("Function")}}</li>
</ul>