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<!DOCTYPE html>
<html class="split chapter"><head><meta charset="utf-8"><title>15.3 Function Objects # Ⓣ Ⓔ ① Ⓐ — Annotated ES5</title><link rel="stylesheet" href="style.css"><link href="x15.2.html" title="15.2 Object Objects " rel="prev">
<link href="spec.html" title="TOC" rel="index">
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</head><body><div class="head">
<h2 id="top">Annotated ECMAScript 5.1 <span id="timestamp"></span></h2>
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<img id="mascot" align="left" src="js-mascot.svg" alt=""><img id="bubble" src="bubble.svg" alt=""></div>
<p id="slogan">‟Ex igne vita”</p>
<div id="annotations"></div>
<script src="timestamp.js"></script></div>
<nav>
<a href="x15.2.html">← 15.2 Object Objects </a> –
<a href="spec.html" class="toc-nav">TOC</a> –
<a href="x15.4.html">15.4 Array Objects →</a>
<ol class="toc"><li><ol><li><a href="x15.3.html#x15.3" id="x15.3-toc">15.3 Function Objects</a>
<b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> <ol><li><a href="x15.3.html#x15.3.1" id="x15.3.1-toc">15.3.1 The Function Constructor Called as a Function</a>
<b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> <ol><li><a href="x15.3.html#x15.3.1.1" id="x15.3.1.1-toc">15.3.1.1 Function (p1, p2, … , pn, body)</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> </li></ol></li><li><a href="x15.3.html#x15.3.2" id="x15.3.2-toc">15.3.2 The Function Constructor</a>
<b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> <ol><li><a href="x15.3.html#x15.3.2.1" id="x15.3.2.1-toc">15.3.2.1 new Function (p1, p2, … , pn, body)</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> </li></ol></li><li><a href="x15.3.html#x15.3.3" id="x15.3.3-toc">15.3.3 Properties of the Function Constructor</a>
<b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> <ol><li><a href="x15.3.html#x15.3.3.1" id="x15.3.3.1-toc">15.3.3.1 Function.prototype</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> </li><li><a href="x15.3.html#x15.3.3.2" id="x15.3.3.2-toc">15.3.3.2 Function.length</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> </li></ol></li><li><a href="x15.3.html#x15.3.4" id="x15.3.4-toc">15.3.4 Properties of the Function Prototype Object</a>
<b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> <ol><li><a href="x15.3.html#x15.3.4.1" id="x15.3.4.1-toc">15.3.4.1 Function.prototype.constructor</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> </li><li><a href="x15.3.html#x15.3.4.2" id="x15.3.4.2-toc">15.3.4.2 Function.prototype.toString ( )</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> </li><li><a href="x15.3.html#x15.3.4.3" id="x15.3.4.3-toc">15.3.4.3 Function.prototype.apply (thisArg, argArray)</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> </li><li><a href="x15.3.html#x15.3.4.4" id="x15.3.4.4-toc">15.3.4.4 Function.prototype.call (thisArg [ , arg1 [ , arg2, … ] ] )</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> </li><li><a href="x15.3.html#x15.3.4.5" id="x15.3.4.5-toc">15.3.4.5 Function.prototype.bind (thisArg [, arg1 [, arg2, …]])</a>
<b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> <ol><li><a href="x15.3.html#x15.3.4.5.1" id="x15.3.4.5.1-toc">15.3.4.5.1 [[Call]]</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> </li><li><a href="x15.3.html#x15.3.4.5.2" id="x15.3.4.5.2-toc">15.3.4.5.2 [[Construct]]</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> </li><li><a href="x15.3.html#x15.3.4.5.3" id="x15.3.4.5.3-toc">15.3.4.5.3 [[HasInstance]] (V)</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> </li></ol></li></ol></li><li><a href="x15.3.html#x15.3.5" id="x15.3.5-toc">15.3.5 Properties of Function Instances</a>
<b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> <ol><li><a href="x15.3.html#x15.3.5.1" id="x15.3.5.1-toc">15.3.5.1 length</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> </li><li><a href="x15.3.html#x15.3.5.2" id="x15.3.5.2-toc">15.3.5.2 prototype</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> </li><li><a href="x15.3.html#x15.3.5.3" id="x15.3.5.3-toc">15.3.5.3 [[HasInstance]] (V)</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> </li><li><a href="x15.3.html#x15.3.5.4" id="x15.3.5.4-toc">15.3.5.4 [[Get]] (P)</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> </li></ol></li></ol></li></ol></li></ol></nav>
<h3 id="x15.3" class="splitme">15.3 Function Objects <a href="#x15.3">#</a> <a href="#x15.3-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h3>
<h4 id="x15.3.1">15.3.1 The Function Constructor Called as a Function <a href="#x15.3.1">#</a> <a href="#x15.3.1-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h4>
<p>
When
<code><b>Function</b></code> is called
as a function rather than as a constructor, it creates and
initialises a new Function object. Thus the function call
<code><b>Function(</b></code><code>…</code><code><b>)</b></code>
is equivalent to the object creation expression <code><b>new
Function(</b></code><code>…</code><code><b>)</b></code>
with the same arguments.</p>
<h5 id="x15.3.1.1">15.3.1.1 Function (p1, p2, … , pn, body) <a href="#x15.3.1.1">#</a> <a href="#x15.3.1.1-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h5>
<p>
When
the <code><b>Function</b></code>
function is called with some arguments <i>p1</i>,
<i>p2</i>, … , <i>pn</i>,
<i>body</i> (where <i>n</i>
might be 0, that is,
there are no “<i>p</i>”
arguments, and where <i>body</i>
might also not be provided), the following steps are taken:</p>
<ol><li><p>
Create
and return a new Function object as if the standard built-in
constructor Function was used in a <b>new </b>expression with the
same arguments (<a href="#x15.3.2.1">15.3.2.1</a>).</p>
</li></ol><h4 id="x15.3.2">15.3.2 The Function Constructor <a href="#x15.3.2">#</a> <a href="#x15.3.2-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h4>
<p>
When
<code><b>Function</b></code> is called
as part of a <code><b>new</b></code>
expression, it is a constructor: it initialises the newly created
object.</p>
<h5 id="x15.3.2.1">15.3.2.1 new Function (p1, p2, … , pn, body) <a href="#x15.3.2.1">#</a> <a href="#x15.3.2.1-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h5>
<p>
The
last argument specifies the body (executable code) of a function;
any preceding arguments specify formal parameters.</p>
<p>
When
the <code><b>Function</b></code>
constructor is called with some arguments <i>p1</i>,
<i>p2</i>, … , <i>pn</i>,
<i>body</i> (where <i>n</i>
might be 0, that is,
there are no “<i>p</i>”
arguments, and where <i>body</i>
might also not be provided), the following steps are taken:</p>
<ol><li><p>
Let
<i>argCount</i> be the total number of arguments passed to this
function invocation.</p>
</li>
<li><p>
Let
<i>P</i> be the empty String.</p>
</li>
<li><p>
If
<i>argCount</i> = 0, let <i>body</i> be the empty String.</p>
</li>
<li><p>
Else
if <i>argCount</i> = 1, let <i>body</i> be that argument.</p>
</li>
<li><p>
Else,
<i>argCount</i> > 1</p>
<ol><li><p>
Let
<i>firstArg</i> be the first argument.</p>
</li>
<li><p>
Let
<i>P</i> be <a href="x9.html#x9.8">ToString</a>(<i>firstArg</i>).</p>
</li>
<li><p>
Let
<i>k</i> be 2.</p>
</li>
<li><p>
Repeat,
while <i>k</i> < <i>argCount</i></p>
<ol><li><p>
Let
<i>nextArg</i> be the <i>k</i>’<sup>th</sup> argument.</p>
</li>
<li><p>
Let
<i>P</i> be the result of concatenating the previous value of <i>P</i>,
the String <code><b>","</b></code>
(a comma), and <a href="x9.html#x9.8">ToString</a>(<i>nextArg</i>).</p>
</li>
<li><p>
Increase
<i>k</i> by 1.</p>
</li></ol></li>
<li><p>
Let
<i>body</i> be the <i>k</i>’<sup>th</sup> argument.</p>
</li></ol></li>
<li><p>
Let
<i>body</i> be <a href="x9.html#x9.8">ToString</a>(<i>body</i>).</p>
</li>
<li><p>
If
<i>P</i> is not parsable as a <i>FormalParameterList</i><sub>opt</sub>
then throw a <b><a href="x15.11.html#x15.11.6.4" class="term-ref">SyntaxError</a></b> exception.</p>
</li>
<li><p>
If
<i>body</i> is not parsable as <i><a href="x13.html#x13">FunctionBody</a></i> then throw a
<b><a href="x15.11.html#x15.11.6.4" class="term-ref">SyntaxError</a></b> exception.</p>
</li>
<li><p>
If<i>body </i>is <a href="x10.html#x10.1.1" class="term-ref">strict mode code</a> (see <a href="x10.html#x10.1.1">10.1.1</a>) then let <i>strict</i> be
<b>true</b>, else let <i>strict</i> be <b>false</b>.</p>
</li>
<li><p>
If
<i>strict</i> is <b>true</b>, throw any exceptions specified in
<a href="x13.html#x13.1">13.1</a> that apply.
</p>
</li>
<li><p>
Return
a new Function object created as specified in <a href="x13.html#x13.2">13.2</a> passing <i>P</i>
as the <i>FormalParameterList</i> and <i>body</i> as the
<i><a href="x13.html#x13">FunctionBody</a></i>. Pass in the <a href="x10.html#x10.2.3">Global Environment</a> as the <i>Scope</i>
parameter and <i>strict</i> as the <i>Strict</i> flag.</p>
</li></ol><p>
A
<code><b>prototype</b></code> property
is automatically created for every function, to provide for the
possibility that the function will be used as a constructor.</p>
<p>
</p><p><b class="note">NOTE</b> It
is permissible but not necessary to have one argument for each
formal parameter to be specified. For example, all three of the
following expressions produce the same result:</p>
<p class="code-example">
<code><b>new
Function("a", "b", "c", "return
a+b+c")</b></code></p>
<p class="code-example">
<code><b>new
Function("a, b, c", "return a+b+c")</b></code></p>
<p class="code-example">
<code><b>new
Function("a,b", "c", "return a+b+c")</b></code></p>
<h4 id="x15.3.3">15.3.3 Properties of the Function Constructor <a href="#x15.3.3">#</a> <a href="#x15.3.3-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h4>
<p>
The
Function constructor is itself a Function object and its [[Class]]
is <code><b>"Function"</b></code>.
The value of the [[Prototype]] internal property of the Function
constructor is the standard built-in Function prototype object
(<a href="#x15.3.4">15.3.4</a>).</p>
<p>
The
value of the [[Extensible]] internal property of the Function
constructor is <b>true</b>.</p>
<p>
The
Function constructor has the following properties:</p>
<h5 id="x15.3.3.1">15.3.3.1 Function.prototype <a href="#x15.3.3.1">#</a> <a href="#x15.3.3.1-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h5>
<p>
The
initial value of <code><b>Function.prototype</b></code>
is the standard built-in Function prototype object (<a href="#x15.3.4">15.3.4</a>).</p>
<p>
This
property has the attributes { [[Writable]]: <b>false</b>,
[[Enumerable]]: <b>false</b>, [[Configurable]]: <b>false</b> }.</p>
<h5 id="x15.3.3.2">15.3.3.2 Function.length <a href="#x15.3.3.2">#</a> <a href="#x15.3.3.2-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h5>
<p>
This
is a data property with a value of 1. This property has the
attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>,
[[Configurable]]: <b>false</b> }.</p>
<h4 id="x15.3.4">15.3.4 Properties of the Function Prototype Object <a href="#x15.3.4">#</a> <a href="#x15.3.4-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h4>
<p>
The
Function prototype object is itself a Function object (its [[Class]]
is <code><b>"Function"</b></code>)
that, when invoked, accepts any arguments and returns <b>undefined</b>.</p>
<p>
The
value of the [[Prototype]] internal property of the Function
prototype object is the standard built-in Object prototype object
(<a href="x15.2.html#x15.2.4">15.2.4</a>). The initial value of the [[Extensible]] internal property
of the Function prototype object is <b>true</b>.</p>
<p>
The
Function prototype object does not have a <code><b>valueOf</b></code>
property of its own; however, it inherits the <code><b>valueOf</b></code>
property from the Object prototype Object.</p>
<p>
The
<code><b>length</b></code> property of
the Function prototype object is <b>0</b>.</p>
<h5 id="x15.3.4.1">15.3.4.1 Function.prototype.constructor <a href="#x15.3.4.1">#</a> <a href="#x15.3.4.1-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h5>
<p>
The
initial value of <code><b>Function.prototype.constructor</b></code>
is the built-in <code><b>Function</b></code>
constructor.</p>
<h5 id="x15.3.4.2">15.3.4.2 Function.prototype.toString ( ) <a href="#x15.3.4.2">#</a> <a href="#x15.3.4.2-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h5>
<p>
An
implementation-dependent representation of the function is returned.
This representation has the syntax of a <i><a href="x13.html#x13">FunctionDeclaration</a></i>.
Note in particular that the use and placement of white space, line
terminators, and semicolons within the representation String is
implementation-dependent.</p>
<p>
The
<code><b>toString</b></code> function
is not generic; it throws a <b><a href="x15.11.html#x15.11.6.5" class="term-ref">TypeError</a></b> exception if its <b>this</b>
value is not a Function object. Therefore, it cannot be transferred
to other kinds of objects for use as a method.</p>
<h5 id="x15.3.4.3">15.3.4.3 Function.prototype.apply (thisArg, argArray) <a href="#x15.3.4.3">#</a> <a href="#x15.3.4.3-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h5>
<p>
When
the <code><b>apply</b></code> method
is called on an object <i>func</i>
with arguments <i>thisArg</i>
and <i>argArray</i>, the
following steps are taken:
</p>
<ol><li><p>
If
<a href="x9.html#x9.11">IsCallable</a>(<i>func</i>) is <b>false</b>, then throw a <b><a href="x15.11.html#x15.11.6.5" class="term-ref">TypeError</a></b>
exception.</p>
</li>
<li><p>
If
<i>argArray</i> is <b>null</b> or <b>undefined</b>, then</p>
<ol><li><p>
Return
the result of calling the [[Call]] internal method of <i>func</i>,
providing <i>thisArg</i> as the <b>this</b> value and an empty
list of arguments.</p>
</li></ol></li>
<li><p>
If
<a href="x8.html#Type">Type</a>(<i>argArray</i>) is not Object, then throw a <b><a href="x15.11.html#x15.11.6.5" class="term-ref">TypeError</a></b>
exception.</p>
</li>
<li><p>
Let
<i>len</i> be the result of calling the [[Get]] internal method of
<i>argArray</i> with argument <code><b>"length"</b></code>.</p>
</li>
<li><p>
Let
<i>n</i> be <a href="x9.html#x9.6">ToUint32</a>(<i>len</i>).</p>
</li>
<li><p>
Let
<i>argList</i> be an empty <a href="x8.html#x8.8">List</a>.</p>
</li>
<li><p>
Let
<i>index</i> be 0.</p>
</li>
<li><p>
Repeat
while <i>index</i> < <i>n</i></p>
<ol><li><p>
Let
<i>indexName</i> be <a href="x9.html#x9.8">ToString</a>(<i>index</i>).</p>
</li>
<li><p>
Let
<i>nextArg</i> be the result of calling the [[Get]] internal
method of <i>argArray</i> with <i>indexName</i> as the argument.</p>
</li>
<li><p>
Append
<i>nextArg</i> as the last element of <i>argList</i>.</p>
</li>
<li><p>
Set
<i>index</i> to <i>index</i> + 1.</p>
</li></ol></li>
<li><p>
Return
the result of calling the [[Call]] internal method of <i>func</i>,
providing <i>thisArg</i> as the <b>this</b> value and <i>argList</i>
as the list of arguments.</p>
</li></ol><p>
The
<code><b>length</b></code> property of
the <code><b>apply</b></code> method
is <b>2</b>.</p>
<p><b class="note">NOTE</b> The
thisArg value is passed without modification as the <b>this</b>
value. This is a change from Edition 3, where a <b>undefined</b> or
<b>null</b> thisArg is replaced with the <a href="x15.1.html#x15.1" class="term-ref">global object</a> and <a href="x9.html#x9.9">ToObject</a>
is applied to all other values and that result is passed as the <b>this</b>
value.</p>
<h5 id="x15.3.4.4">15.3.4.4 Function.prototype.call (thisArg [ , arg1 [ , arg2, … ] ] ) <a href="#x15.3.4.4">#</a> <a href="#x15.3.4.4-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h5>
<p>
When
the <code><b>call</b></code> method is
called on an object <i>func</i>
with argument <i>thisArg</i>
and optional arguments <i>arg1</i>,
<i>arg2</i> etc, the
following steps are taken:</p>
<ol><li><p>
If
<a href="x9.html#x9.11">IsCallable</a>(<i>func</i>) is <b>false</b>, then throw a <b><a href="x15.11.html#x15.11.6.5" class="term-ref">TypeError</a></b>
exception.</p>
</li>
<li><p>
Let
<i>argList</i> be an empty <a href="x8.html#x8.8">List</a>.</p>
</li>
<li><p>
If
this method was called with more than one argument then in left to
right order starting with <i>arg1</i> append each argument as the
last element of <i>argList</i></p>
</li>
<li><p>
Return
the result of calling the [[Call]] internal method of <i>func</i>,
providing <i>thisArg</i> as the <b>this</b> value and <i>argList</i>
as the list of arguments.</p>
</li></ol><p>
The
<code><b>length</b></code> property of
the <code><b>call</b></code> method is
<b>1</b>.</p>
<p><b class="note">NOTE</b> The
thisArg value is passed without modification as the <b>this</b>
value. This is a change from Edition 3, where a <b>undefined</b> or
<b>null</b> thisArg is replaced with the <a href="x15.1.html#x15.1" class="term-ref">global object</a> and <a href="x9.html#x9.9">ToObject</a>
is applied to all other values and that result is passed as the <b>this</b>
value.</p>
<h5 id="x15.3.4.5">15.3.4.5 Function.prototype.bind (thisArg [, arg1 [, arg2, …]]) <a href="#x15.3.4.5">#</a> <a href="#x15.3.4.5-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h5>
<p>
The
bind method takes one or more arguments, <i>thisArg</i>
and (optionally) <i>arg1</i>,
<i>arg2</i>, etc, and
returns a new function object by performing the following steps:</p>
<ol><li><p>
Let
<i>Target </i>be the <b>this </b>value.</p>
</li>
<li><p>
If
<a href="x9.html#x9.11">IsCallable</a>(<i>Target</i>) is <b>false</b>, throw a <b>TypeError
</b>exception.</p>
</li>
<li><p>
Let
<i>A </i>be a new (possibly empty) internal list of all of the
argument values provided after <i>thisArg </i>(<i>arg1</i>, <i>arg2</i>
etc), in order.</p>
</li>
<li><p>
Let
<i>F</i> be a new native ECMAScript object .</p>
</li>
<li><p>
Set
all the internal methods, except for [[Get]], of <i>F</i> as
specified in <a href="x8.html#x8.12">8.12</a>.</p>
</li>
<li><p>
Set
the [[Get]] internal property of <i>F </i>as specified in <a href="#x15.3.5.4">15.3.5.4</a>.</p>
</li>
<li><p>
Set
the [[TargetFunction]] internal property of <i>F </i>to <i>Target</i>.</p>
</li>
<li><p>
Set
the [[BoundThis]] internal property of <i>F</i> to the value of
<i>thisArg</i>.</p>
</li>
<li><p>
Set
the [[BoundArgs]] internal property of <i>F </i>to <i>A</i>.</p>
</li>
<li><p>
Set
the [[Class]] internal property of <i>F</i> to <b>"Function"</b>.</p>
</li>
<li><p>
Set
the [[Prototype]] internal property of <i>F </i>to the standard
built-in Function prototype object as specified in <a href="#x15.3.3.1">15.3.3.1</a>.</p>
</li>
<li><p>
Set
the [[Call]] internal property of <i>F </i>as described in
<a href="#x15.3.4.5.1">15.3.4.5.1</a>.</p>
</li>
<li><p>
Set
the [[Construct]] internal property of <i>F </i>as described in
<a href="#x15.3.4.5.2">15.3.4.5.2</a>.</p>
</li>
<li><p>
Set
the [[HasInstance]] internal property of <i>F </i>as described in
<a href="#x15.3.4.5.3">15.3.4.5.3</a>.</p>
</li>
<li><p>
If
the [[Class]] internal property of <i>Target </i>is <b>"Function"</b>,
then</p>
<ol><li><p>
Let
<i>L </i>be the <b>length </b>property of <i>Target </i>minus the
length of <i>A</i>.</p>
</li>
<li><p>
Set
the <b>length </b>own property of <i>F </i>to either 0 or
<i>L</i>, whichever is larger.
</p>
</li></ol></li>
<li><p>
Else
set the <b>length </b>own property of <i>F </i>to 0.</p>
</li>
<li><p>
Set
the attributes of the <b>length</b> own property of <i>F</i> to
the values specified in <a href="#x15.3.5.1">15.3.5.1</a>.</p>
</li>
<li><p>
Set
the [[Extensible]] internal property of <i>F</i> to <b>true</b>.</p>
</li>
<li><p>
Let
<i>thrower</i> be the [[ThrowTypeError]] function Object (<a href="x13.html#x13.2.3">13.2.3</a>).</p>
</li>
<li><p>
Call
the [[DefineOwnProperty]] internal method of <i>F</i> with
arguments <code><b>"caller"</b></code>,
PropertyDescriptor {[[Get]]: <i>thrower</i>, [[Set]]: <i>thrower</i>,
[[Enumerable]]: <b>false</b>, [[Configurable]]:<b> false</b>}, and
<b>false</b>.</p>
</li>
<li><p>
Call
the [[DefineOwnProperty]] internal method of <i>F</i> with
arguments <code><b>"arguments"</b></code>,
PropertyDescriptor {[[Get]]: <i>thrower</i>, [[Set]]: <i>thrower</i>,
[[Enumerable]]: <b>false</b>, [[Configurable]]: <b>false</b>}, and
<b>false</b>.</p>
</li>
<li><p>
Return
<i>F</i>.</p>
</li></ol><p>
The
<code><b>length</b></code> property of
the <code><b>bind</b></code> method is
<b>1</b>.</p>
<p><b class="note">NOTE</b> Function
objects created using <code><b>Function.prototype.bind</b></code>
do not have a <code><b>prototype</b></code>
property or the [[Code]], [[FormalParameters]], and [[Scope]]
internal properties.</p>
<h6 id="x15.3.4.5.1">15.3.4.5.1 [[Call]] <a href="#x15.3.4.5.1">#</a> <a href="#x15.3.4.5.1-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h6>
<p>
When
the [[Call]] internal method of a function object, <i>F</i>,
which was created using the bind function is called with a <b>this</b>
value and a list of arguments <i>ExtraArgs</i>,
the following steps are taken:</p>
<ol><li><p>
Let
<i>boundArgs</i> be the value of <i>F’s</i> [[BoundArgs]]
internal property.</p>
</li>
<li><p>
Let
<i>boundThis</i> be the value of <i>F’s</i> [[BoundThis]]
internal property.</p>
</li>
<li><p>
Let
<i>target</i> be the value of <i>F’s</i> [[TargetFunction]]
internal property.</p>
</li>
<li><p>
Let
<i>args</i> be a new list containing the same values as the list
<i>boundArgs</i> in the same order followed by the same values as
the list <i>ExtraArgs</i> in the same order.</p>
</li>
<li><p>
Return
the result of calling the [[Call]] internal method of <i>target</i>
providing <i>boundThis</i> as the <b>this </b>value and providing
<i>args</i> as the arguments.</p>
</li></ol><h6 id="x15.3.4.5.2">15.3.4.5.2 [[Construct]] <a href="#x15.3.4.5.2">#</a> <a href="#x15.3.4.5.2-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h6>
<p>
When
the [[Construct]] internal method of a function object, <i>F</i>
that was created using the bind function is called with a list of
arguments <i>ExtraArgs</i>,
the following steps are taken:</p>
<ol><li><p>
Let
<i>target</i> be the value of <i>F’s</i> [[TargetFunction]]
internal property.</p>
</li>
<li><p>
If
<i>target</i> has no [[Construct]] internal method, a <b><a href="x15.11.html#x15.11.6.5" class="term-ref">TypeError</a></b>
exception is thrown.</p>
</li>
<li><p>
Let
<i>boundArgs</i> be the value of <i>F’s</i> [[BoundArgs]]
internal property.</p>
</li>
<li><p>
Let
<i>args</i> be a new list containing the same values as the list
<i>boundArgs</i> in the same order followed by the same values as
the list <i>ExtraArgs</i> in the same order.</p>
</li>
<li><p>
Return
the result of calling the [[Construct]] internal method of<i>target</i> providing <i>args</i> as the arguments.</p>
</li></ol><h6 id="x15.3.4.5.3">15.3.4.5.3 [[HasInstance]] (V) <a href="#x15.3.4.5.3">#</a> <a href="#x15.3.4.5.3-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h6>
<p>
When
the [[HasInstance]] internal method of a function object <i>F</i>,
that was created using the bind function is called with argument <i>V</i>,
the following steps are taken:</p>
<ol><li><p>
Let
<i>target</i> be the value of <i>F’s</i> [[TargetFunction]]
internal property.</p>
</li>
<li><p>
If
<i>target</i> has no [[HasInstance]] internal method, a <b><a href="x15.11.html#x15.11.6.5" class="term-ref">TypeError</a></b>
exception is thrown.</p>
</li>
<li><p>
Return
the result of calling the [[HasInstance]] internal method of<i>target</i> providing <i>V</i> as the argument.</p>
</li></ol><h4 id="x15.3.5">15.3.5 Properties of Function Instances <a href="#x15.3.5">#</a> <a href="#x15.3.5-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h4>
<p>
In
addition to the required internal properties, every function
instance has a [[Call]] internal property and in most cases use a
different version of the [[Get]] internal property. Depending on how
they are created (see <a href="x8.html#x8.6.2">8.6.2</a> ,<a href="x13.html#x13.2">13.2</a>, 15, and <a href="#x15.3.4.5">15.3.4.5</a>), function
instances may have a [[HasInstance]] internal property, a [[Scope]]
internal property, a [[Construct]] internal property, a
[[FormalParameters]] internal property, a [[Code]] internal
property, a [[TargetFunction]] internal property, a [[BoundThis]]
internal property, and a [[BoundArgs]] internal property.</p>
<p>
The
value of the [[Class]] internal property is <b>"Function"</b>.</p>
<p>
Function
instances that correspond to strict mode functions (<a href="x13.html#x13.2">13.2</a>) and
function instances created using the <b>Function.prototype.bind
method</b> (<a href="#x15.3.4.5">15.3.4.5</a>) have properties named “caller” and
“arguments” that throw a <b><a href="x15.11.html#x15.11.6.5" class="term-ref">TypeError</a></b> exception. An
ECMAScript implementation must not associate any implementation
specific behaviour with accesses of these properties from strict
mode <a href="x10.html#function-code">function code</a>.
</p>
<h5 id="x15.3.5.1">15.3.5.1 length <a href="#x15.3.5.1">#</a> <a href="#x15.3.5.1-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h5>
<p>
The
value of the <code><b>length</b></code>
property is an integer that indicates the “typical” number of
arguments expected by the function. However, the language permits
the function to be invoked with some other number of arguments. The
behaviour of a function when invoked on a number of arguments other
than the number specified by its <code><b>length</b></code>
property depends on the function. This property has the attributes
{ [[Writable]]: <b>false</b>,
[[Enumerable]]: <b>false</b>,
[[Configurable]]: <b>false</b> }.</p>
<h5 id="x15.3.5.2">15.3.5.2 prototype <a href="#x15.3.5.2">#</a> <a href="#x15.3.5.2-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h5>
<p>
The
value of the <code><b>prototype</b></code>
property is used to initialise the [[Prototype]] internal property
of a newly created object before the Function object is invoked as a
constructor for that newly created object. This property has the
attribute { [[Writable]]: <b>true</b>,
[[Enumerable]]: <b>false</b>,
[[Configurable]]: <b>false</b>
}.</p>
<p><b class="note">NOTE</b> Function
objects created using <code><b><a href="#x15.3.4.5">Function.prototype.bind</a></b></code>
do not have a <code><b>prototype</b></code>
property.</p>
<h5 id="x15.3.5.3">15.3.5.3 [[HasInstance]] (V) <a href="#x15.3.5.3">#</a> <a href="#x15.3.5.3-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h5>
<p>
Assume
<i>F</i> is a Function
object.</p>
<p>
When
the [[HasInstance]] internal method of <i>F</i>
is called with value <i>V</i>,
the following steps are taken:</p>
<ol><li><p>
If
<i>V</i> is not an object, return <b>false</b>.</p>
</li>
<li><p>
Let
<i>O</i> be the result of calling the [[Get]] internal method of <i>F</i>
with property name <code><b>"prototype"</b></code>.</p>
</li>
<li><p>
If
<a href="x8.html#Type">Type</a>(<i>O</i>) is not Object, throw a <b><a href="x15.11.html#x15.11.6.5" class="term-ref">TypeError</a></b> exception.</p>
</li>
<li><p>
Repeat</p>
<ol><li><p>
Let
<i>V</i> be the value of the [[Prototype]] internal property of <i>V</i>.</p>
</li>
<li><p>
If
<i>V</i> is <code><b>null</b></code>,
return <b>false</b>.</p>
</li>
<li><p>
If
<i>O</i> and <i>V</i> refer to the same object, return <b>true</b>.</p>
</li></ol></li></ol><p class="sp">
</p><p><b class="note">NOTE</b> Function
objects created using <code><b><a href="#x15.3.4.5">Function.prototype.bind</a></b></code>
have a different implementation of [[HasInstance]] defined in
<a href="#x15.3.4.5.3">15.3.4.5.3</a>.</p>
<h5 id="x15.3.5.4">15.3.5.4 [[Get]] (P) <a href="#x15.3.5.4">#</a> <a href="#x15.3.5.4-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h5>
<p>
Function
objects use a variation of the [[Get]] internal method used for
other native ECMAScript objects (<a href="x8.html#x8.12.3">8.12.3</a>).</p>
<p>
Assume
<i>F</i> is a Function
object. When the [[Get]] internal method of <i>F</i>
is called with property name <i>P</i>,
the following steps are taken:</p>
<ol><li><p>
Let
<i>v</i> be the result of calling the default [[Get]] internal
method (<a href="x8.html#x8.12.3">8.12.3</a>) on <i>F</i> passing <i>P</i> as the property name
argument.</p>
</li>
<li><p>
If
<i>P</i> is <code><b>"caller"
</b></code>and <i>v</i> is a strict mode Function object, throw a
<b><a href="x15.11.html#x15.11.6.5" class="term-ref">TypeError</a></b> exception.
</p>
</li>
<li><p>
Return
<i>v</i>.</p>
</li></ol><p><b class="note">NOTE</b> Function
objects created using <code><b><a href="#x15.3.4.5">Function.prototype.bind</a></b></code>
use the default [[Get]] internal method.</p>
</body><script src="anno.js"></script></html>