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<!DOCTYPE html>
<html class="split chapter"><head><meta charset="utf-8"><title>15.12 The JSON Object # Ⓣ Ⓔ ① Ⓐ — Annotated ES5</title><link rel="stylesheet" href="style.css"><link href="x15.11.html" title="15.11 Error Objects " rel="prev">
<link href="spec.html" title="TOC" rel="index">
<link href="x16.html" title="16 Errors " rel="next">
</head><body><div class="head">
<h2 id="top">Annotated ECMAScript 5.1 <span id="timestamp"></span></h2>
<div id="mascot-treehouse">
<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="x15.11.html">← 15.11 Error Objects </a> –
<a href="spec.html" class="toc-nav">TOC</a> –
<a href="x16.html">16 Errors →</a>
<ol class="toc"><li><ol><li><a href="x15.12.html#x15.12" id="x15.12-toc">15.12 The JSON Object</a>
<b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> <ol><li><a href="x15.12.html#x15.12.1" id="x15.12.1-toc">15.12.1 The JSON Grammar </a>
<b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> <ol><li><a href="x15.12.html#x15.12.1.1" id="x15.12.1.1-toc">15.12.1.1 The JSON Lexical Grammar</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> </li><li><a href="x15.12.html#x15.12.1.2" id="x15.12.1.2-toc">15.12.1.2 The JSON Syntactic Grammar</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> </li></ol></li><li><a href="x15.12.html#x15.12.2" id="x15.12.2-toc">15.12.2 parse ( text [ , reviver ] )</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> </li><li><a href="x15.12.html#x15.12.3" id="x15.12.3-toc">15.12.3 stringify ( value [ , replacer [ , space ] ] )</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b> </li></ol></li></ol></li></ol></nav>
<h3 id="x15.12" class="splitme">15.12 The JSON Object <a href="#x15.12">#</a> <a href="#x15.12-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h3>
<p>
The
<b>JSON</b> object is a single object that contains two functions,
<b>parse </b>and <b>stringify</b>, that are used to parse and
construct JSON texts. The JSON Data Interchange Format is described
in RFC 4627 <<a href="http://www.ietf.org/rfc/rfc4627.txt">http://www.ietf.org/rfc/rfc4627.txt</a>>. The JSON
interchange format used in this specification is exactly that
described by RFC 4627 with two exceptions:</p>
<ul><li><p>
The
top level <i>JSONText</i>
production of the ECMAScript JSON grammar may consist of any
<i>JSONValue</i> rather
than being restricted to being a <i>JSONObject</i>
or a <i>JSONArray</i> as
specified by RFC 4627.
</p>
</li>
<li><p>
Conforming
implementations of <b>JSON.parse</b> and <b>JSON.stringify</b> must
support the exact interchange format described in this
specification without any deletions or extensions to the format.
This differs from RFC 4627 which permits a JSON parser to accept
non-JSON forms and extensions.</p>
</li></ul><p>
The
value of the [[Prototype]] internal property of the JSON object is
the standard built-in Object prototype object (<a href="x15.2.html#x15.2.4">15.2.4</a>). The value of
the [[Class]] internal property of the JSON object is <code><b>"JSON"</b></code>.
The value of the [[Extensible]] internal property of the JSON object
is set to <b>true</b>.</p>
<p>
The
JSON object does not have a [[Construct]] internal property; it is
not possible to use the JSON object as a constructor with the <code><b>new</b></code>
operator.</p>
<p>
The
JSON object does not have a [[Call]] internal property; it is not
possible to invoke the JSON object as a function.</p>
<h4 id="x15.12.1">15.12.1 The JSON Grammar <a href="#x15.12.1">#</a> <a href="#x15.12.1-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h4>
<p>
JSON.stringify
produces a String that conforms to the following JSON grammar.
JSON.parse accepts a String that conforms to the JSON grammar.</p>
<h5 id="x15.12.1.1">15.12.1.1 The JSON Lexical Grammar <a href="#x15.12.1.1">#</a> <a href="#x15.12.1.1-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h5>
<p>
JSON
is similar to ECMAScript source text in that it consists of a
sequence of characters conforming to the rules of <i>SourceCharacter</i>.
The JSON Lexical Grammar defines the tokens that make up a JSON text
similar to the manner that the ECMAScript lexical grammar defines
the tokens of an ECMAScript source test. The JSON Lexical grammar
only recognizes the white space character specified by the
production <i>JSONWhiteSpace</i>.
The JSON lexical grammar shares some productions with the
ECMAScript lexical grammar. All nonterminal symbols of the grammar
that do not begin with the characters “JSON” are defined by
productions of the ECMAScript lexical grammar.</p>
<p class="tiny-btm">
<b>Syntax</b></p>
<p class="keep">
<i>JSONWhiteSpace </i><b>::</b></p>
<p class="def1">
<TAB><br><CR><br><LF><br><SP></p>
<p class="keep">
<i>JSONString </i><b>::</b></p>
<p class="def1">
<code><b>"</b></code> <i>JSONStringCharacters</i><sub>opt</sub><code><b>"</b></code></p>
<p class="keep">
<i>JSONStringCharacters </i><b>::</b></p>
<p class="def1">
<i>JSONStringCharacter
JSONStringCharacters</i><sub>opt</sub></p>
<p>
<i>JSONStringCharacter </i><b>::</b></p>
<p class="def1">
<i>SourceCharacter </i><b>but
not</b><i> double-quote </i><code><b>"</b></code> <b>or</b><i>backslash </i><code><b>\
</b></code><b>or</b><i>U+0000 thru U+001F</i></p>
<p class="def1">
<code><b>\</b></code> <i>JSONEscapeSequence</i></p>
<p class="keep">
<i>JSONEscapeSequence </i><b>::</b></p>
<p class="def1">
<i>JSONEscapeCharacter</i></p>
<p class="def1">
<i>UnicodeEscapeSequence </i>
</p>
<p class="keep">
<i>JSONEscapeCharacter </i><b>::</b> <b>one
of</b></p>
<p class="def1">
<code><b>"
/ \ b f n r t</b></code></p>
<p class="keep">
<i>JSONNumber </i><b>::</b></p>
<p class="def1">
<code><b>-</b></code><sub>opt</sub><i>DecimalIntegerLiteral JSONFraction</i><sub>opt</sub><i>ExponentPart</i><sub>opt</sub></p>
<p class="keep">
<i>JSONFraction </i><b>::</b></p>
<p class="def1">
<code><b>.</b></code> <i>DecimalDigits</i></p>
<p class="keep">
<i>JSONNullLiteral </i><b>::</b></p>
<p class="def1">
<i>NullLiteral</i></p>
<p class="keep">
<i>JSONBooleanLiteral </i><b>::</b></p>
<p class="def1">
<i>BooleanLiteral</i></p>
<h5 id="x15.12.1.2">15.12.1.2 The JSON Syntactic Grammar <a href="#x15.12.1.2">#</a> <a href="#x15.12.1.2-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h5>
<p>
The
JSON Syntactic Grammar defines a valid JSON text in terms of tokens
defined by the JSON lexical grammar. The goal symbol of the grammar
is <i>JSONText</i>.
</p>
<p class="tiny-btm">
<b>Syntax</b></p>
<p class="keep">
<i>JSONText </i><b>:</b><i> </i>
</p>
<p class="def1">
<i>JSONValue</i></p>
<p class="keep">
<i>JSONValue </i><b>:</b><i> </i>
</p>
<p class="def1">
<i>JSONNullLiteral<br>JSONBooleanLiteral<br>JSONObject<br>JSONArray<br>JSONString<br>JSONNumber</i></p>
<p class="keep">
<i>JSONObject </i><b>:</b></p>
<p class="def1">
<code><b>{
}</b></code> <i><br></i><code><b>{</b></code> <i>JSONMemberList </i><code><b>}</b></code></p>
<p class="keep">
<i>JSONMember </i><b>:</b></p>
<p class="def1">
<i>JSONString </i><code><b>:</b></code> <i>JSONValue</i></p>
<p class="keep">
<i>JSONMemberList </i><b>:</b></p>
<p class="def1">
<i>JSONMember
<br>JSONMemberList </i><code><b>,</b></code> <i><b>
</b>JSONMember </i>
</p>
<p class="keep">
<i>JSONArray </i><b>:</b></p>
<p class="def1">
<code><b>[
]</b></code> <i><br></i><code><b>[</b></code> <i>JSONElementList</i><code><b>
]</b></code></p>
<p class="keep">
<i>JSONElementList </i><b>:</b></p>
<p class="def1">
<i>JSONValue<br>JSONElementList</i><code><b>
,</b></code> <i> JSONValue</i></p>
<h4 id="x15.12.2">15.12.2 parse ( text [ , reviver ] ) <a href="#x15.12.2">#</a> <a href="#x15.12.2-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h4>
<p>
The
<code><b>parse</b></code> function
parses a JSON text (a JSON-formatted String) and produces an
ECMAScript value. The JSON format is a restricted form of ECMAScript
literal. JSON objects are realized as ECMAScript objects. JSON
arrays are realized as ECMAScript arrays. JSON strings, numbers,
booleans, and null are realized as ECMAScript Strings, Numbers,
Booleans, and <b>null</b>. JSON uses a more limited set of white
space characters than <i><a href="x7.html#WhiteSpace">WhiteSpace</a></i>
and allows Unicode code points U+2028 and U+2029 to directly appear
in <i>JSONString</i>
literals without using an escape sequence. The process of parsing is
similar to <a href="x11.html#x11.1.4">11.1.4</a> and <a href="x11.html#x11.1.5">11.1.5</a> as constrained by the JSON grammar.</p>
<p>
The
optional <i>reviver</i> parameter is a function that takes two
parameters, (<i>key</i> and <i>value</i>). It can filter and
transform the results. It is called with each of the <i>key</i>/<i>value</i>
pairs produced by the parse, and its return value is used instead of
the original value. If it returns what it received, the structure is
not modified. If it returns <b>undefined</b> then the property is
deleted from the result.</p>
<ol><li><p>
Let
<i>JText</i> be <a href="x9.html#x9.8">ToString</a>(<i>text</i>).</p>
</li>
<li><p>
Parse
<i>JText</i> using the grammars in <a href="#x15.12.1">15.12.1</a>. Throw a <b><a href="x15.11.html#x15.11.6.4" class="term-ref">SyntaxError</a></b>
exception if <i>JText</i> did not conform to the JSON grammar for
the goal symbol <i>JSONText</i>.
</p>
</li>
<li><p>
Let
<i>unfiltered</i> be the result of parsing and evaluating <i>JText</i>
as if it was the source text of an ECMAScript <i><a href="x14.html#x14">Program</a></i> but
using<i> JSONString </i>in place<i> </i>of<i> <a href="x7.html#x7.8.4">StringLiteral</a></i>.
Note that since <i>JText</i> conforms to the JSON grammar this
result will be either a <a href="x4.html#primitive_value" class="term-ref">primitive value</a> or an object that is
defined by either an <i>ArrayLiteral</i> or an <i>ObjectLiteral</i>.</p>
</li>
<li><p>
If
<a href="x9.html#x9.11">IsCallable</a>(<i>reviver</i>) is <b>true</b>, then</p>
<ol><li><p>
Let
<i>root</i> be a new object created as if by the expression <code><b>new
Object()</b></code>, where <code><b>Object</b></code>
is the standard built-in constructor with that name.</p>
</li>
<li><p>
Call
the [[DefineOwnProperty]] internal method of <i>root</i> with the
empty String, the PropertyDescriptor {[[Value]]: <i>unfiltered</i>,
[[Writable]]: <b>true</b>, [[Enumerable]]: <b>true</b>,
[[Configurable]]: <b>true</b>}, and <b>false</b> as arguments.</p>
</li>
<li><p>
Return
the result of calling the abstract operation <a href="#Walk">Walk</a>, passing <i>root</i>
and the empty String. The abstract operation <a href="#Walk">Walk</a> is described
below.</p>
</li></ol></li>
<li><p>
Else</p>
<ol><li><p>
Return
<i>unfiltered</i>.</p>
</li></ol></li></ol><p>
The
abstract operation <dfn id="Walk">Walk</dfn> is a recursive abstract operation that takes
two parameters: a <i>holder</i>
object and the String <i>name</i>
of a property in that object. Walk uses the value of <i>reviver</i>
that was originally passed to the above parse function.</p>
<ol><li><p>
Let
<i>val</i> be the result of calling the [[Get]] internal method of
<i>holder</i> with argument <i>name</i>.</p>
</li>
<li><p>
If
<i>val</i> is an object, then</p>
<ol><li><p>
If
the [[Class]] internal property of <i>val</i> is <code><b>"Array"</b></code></p>
<ol><li><p>
Set
<i>I</i> to 0.</p>
</li>
<li><p>
Let
<i>len</i> be the result of calling the [[Get]] internal method
of <i>val</i> with argument <code><b>"length"</b></code>.</p>
</li>
<li><p>
Repeat
while <i>I </i>< <i>len</i>,
</p>
<ol><li><p>
Let
<i>newElement</i> be the result of calling the abstract
operation <a href="#Walk">Walk</a>, passing <i>val</i> and <a href="x9.html#x9.8">ToString</a>(<i>I</i>).</p>
</li>
<li><p>
If
<i>newElement</i> is <b>undefined</b>, then</p>
<ol><li><p>
Call
the [[Delete]] internal method of <i>val</i> with <a href="x9.html#x9.8">ToString</a>(<i>I</i>)
and <b>false</b> as arguments.
</p>
</li></ol></li>
<li><p>
Else</p>
<ol><li><p>
Call
the [[DefineOwnProperty]] internal method of <i>val</i> with
arguments <a href="x9.html#x9.8">ToString</a>(<i>I</i>), the <a href="x8.html#x8.10">Property Descriptor</a>
{[[Value]]: <i>newElement</i>, [[Writable]]: true,
[[Enumerable]]: true, [[Configurable]]: true}, and <b>false</b>.</p>
</li></ol></li>
<li><p>
Add
1 to <i>I</i>.</p>
</li></ol></li></ol></li>
<li><p>
Else</p>
<ol><li><p>
Let
<i>keys</i> be an internal <a href="x8.html#x8.8">List</a> of String values consisting of
the names of all the own properties of <i>val</i> whose
[[Enumerable]] attribute is <b>true</b>. The ordering of the
Strings should be the same as that used by the
<b><a href="x15.2.html#x15.2.3.14">Object.keys</a></b>
standard built-in function.</p>
</li>
<li><p>
For
each String <i>P</i> in <i>keys</i> do,
</p>
<ol><li><p>
Let
<i>newElement</i> be the result of calling the abstract
operation <a href="#Walk">Walk</a>, passing <i>val</i> and <i>P</i>.
</p>
</li>
<li><p>
If
<i>newElement</i> is <b>undefined</b>, then</p>
<ol><li><p>
Call
the [[Delete]] internal method of <i>val</i> with <i>P</i> and
<b>false</b> as arguments.
</p>
</li></ol></li>
<li><p>
Else</p>
<ol><li><p>
Call
the [[DefineOwnProperty]] internal method of <i>val</i> with
arguments <i>P</i>, the <a href="x8.html#x8.10">Property Descriptor</a> {[[Value]]:
<i>newElement</i>, [[Writable]]: <b>true</b>, [[Enumerable]]:
<b>true</b>, [[Configurable]]: <b>true</b>}, and <b>false</b>.</p>
</li></ol></li></ol></li></ol></li></ol></li>
<li><p>
Return
the result of calling the [[Call]] internal method of <i>reviver</i>
passing <i>holder</i> as the <b>this</b> value and with an argument
list consisting of <i>name </i>and <i>val</i>.</p>
</li></ol><p>
It is
not permitted for a conforming implementation of <code><b>JSON.parse</b></code>
to extend the JSON grammars. If an implementation wishes to support
a modified or extended JSON interchange format it must do so by
defining a different parse function.
</p>
<p><b class="note">NOTE</b> In
the case where there are duplicate name Strings within an object,
lexically preceding values for the same key shall be overwritten.</p>
<h4 id="x15.12.3">15.12.3 stringify ( value [ , replacer [ , space ] ] ) <a href="#x15.12.3">#</a> <a href="#x15.12.3-toc" class="bak">Ⓣ</a> <b class="erra">Ⓔ</b> <b class="rev1">①</b> <b class="anno">Ⓐ</b></h4>
<p>
The
<code><b>stringify</b></code> function
returns a String in JSON format representing an ECMAScript value. It
can take three parameters. The first parameter is required. The
<i>value</i> parameter is
an ECMAScript value, which is usually an object or array, although
it can also be a String, Boolean, Number or <b>null</b>. The
optional <i>replacer</i>
parameter is either a function that alters the way objects and
arrays are stringified, or an array of Strings and Numbers that acts
as a white list for selecting the object properties that will be
stringified. The optional <i>space</i>
parameter is a String or Number that allows the result to have white
space injected into it to improve human readability.</p>
<p>
These
are the steps in stringifying an object:</p>
<ol><li><p>
Let
<i>stack</i> be an empty <a href="x8.html#x8.8">List</a>.</p>
</li>
<li><p>
Let
<i>indent</i> be the empty String.</p>
</li>
<li><p>
Let
<i>PropertyList</i> and <i>ReplacerFunction</i> be <b>undefined</b>.</p>
</li>
<li><p>
If
<a href="x8.html#Type">Type</a>(<i>replacer</i>) is Object, then</p>
<ol><li><p>
If
<a href="x9.html#x9.11">IsCallable</a>(<i>replacer</i>) is <b>true</b>, then</p>
<ol><li><p>
Let
<i>ReplacerFunction </i>be<i> replacer</i>.</p>
</li></ol></li>
<li><p>
Else
if the [[Class]] internal property of <i>replacer</i> is <code><b>"Array"</b></code>,
then</p>
<ol><li><p>
Let
<i>PropertyList </i> be an empty internal <a href="x8.html#x8.8">List</a></p>
</li>
<li><p>
For
each value <i>v</i> of a property of <i>replacer</i> that has an
array index property name. The properties are enumerated in the
ascending array index order of their names.</p>
<ol><li><p>
Let
<i>item</i> be <b>undefined</b>.</p>
</li>
<li><p>
If
<a href="x8.html#Type">Type</a>(<i>v</i>) is String then let <i>item</i> be <i>v.</i></p>
</li>
<li><p>
Else
if <a href="x8.html#Type">Type</a>(<i>v</i>) is Number then let <i>item</i> be <a href="x9.html#x9.8">ToString</a>(<i>v</i>).</p>
</li>
<li><p>
Else
if <a href="x8.html#Type">Type</a>(<i>v</i>) is Object then,</p>
<ol><li><p>
If
the [[Class]] internal property of <i>v</i> is <code><b>"String"</b></code>
or <code><b>"Number"
</b></code>then let <i>item</i> be <a href="x9.html#x9.8">ToString</a>(<i>v</i>).</p>
</li></ol></li>
<li><p>
If
<i>item</i> is not undefined and <i>item</i> is not currently an
element of <i>PropertyList</i> then,</p>
<ol><li><p>
Append
<i>item</i> to the end of <i>PropertyList</i>.</p>
</li></ol></li></ol></li></ol></li></ol></li>
<li><p>
If
<a href="x8.html#Type">Type</a>(<i>space</i>) is Object then,</p>
<ol><li><p>
If
the [[Class]] internal property of <i>space</i> is <code><b>"Number"</b></code>
then,</p>
<ol><li><p>
Let
<i>space</i> be <a href="x9.html#x9.3">ToNumber</a>(<i>space</i>).</p>
</li></ol></li>
<li><p>
Else
if the [[Class]] internal property of <i>space</i> is <code><b>"String"</b></code>
then,</p>
<ol><li><p>
Let
<i>space</i> be <a href="x9.html#x9.8">ToString</a>(<i>space</i>).</p>
</li></ol></li></ol></li>
<li><p>
If
<a href="x8.html#Type">Type</a>(<i>space</i>) is Number</p>
<ol><li><p>
Let
<i>space</i> be min(10, <a href="x9.html#x9.4">ToInteger</a>(<i>space</i>)).</p>
</li>
<li><p>
Set
<i>gap</i> to a String containing <i>space</i> space characters.
This will be the empty String if <i>space</i> is less than 1.</p>
</li></ol></li>
<li><p>
Else
if <a href="x8.html#Type">Type</a>(<i>space)</i> is String</p>
<ol><li><p>
If
the number of characters in <i>space</i> is 10 or less, set <i>gap</i>
to <i>space</i> otherwise set <i>gap</i> to a String consisting of
the first 10 characters of <i>space</i>.</p>
</li></ol></li>
<li><p>
Else</p>
<ol><li><p>
Set
<i>gap</i> to the empty String.</p>
</li></ol></li>
<li><p>
Let
<i>wrapper</i> be a new object created as if by the expression <code><b>new
Object()</b></code>, where <code><b>Object</b></code>
is the standard built-in constructor with that name.</p>
</li>
<li><p>
Call
the [[DefineOwnProperty]] internal method of <i>wrapper</i> with
arguments the empty String, the <a href="x8.html#x8.10">Property Descriptor</a> {[[Value]]:
<i>value</i>, [[Writable]]: <b>true</b>, [[Enumerable]]: <b>true</b>,
[[Configurable]]: <b>true</b>}, and <b>false</b>.</p>
</li>
<li><p>
Return
the result of calling the abstract operation <a href="#Str"><i>Str</i></a> with the
empty String and <i>wrapper</i>.</p>
</li></ol><p>
The
abstract operation <dfn id="Str"><i>Str</i>(<i>key</i>,
<i>holder</i>)</dfn>
has access to <i>ReplacerFunction </i>from the invocation of the <code><b>stringify</b></code>
method. Its algorithm is as follows:</p>
<ol><li><p>
Let
<i>value</i> be the result of calling the [[Get]] internal method
of <i>holder</i> with argument <i>key</i>.</p>
</li>
<li><p>
If
<a href="x8.html#Type">Type</a>(<i>value</i>) is Object, then</p>
<ol><li><p>
Let
<i>toJSON</i> be the result of calling the [[Get]] internal method
of <i>value</i> with argument <code><b>"toJSON"</b></code>.</p>
</li>
<li><p>
If
<a href="x9.html#x9.11">IsCallable</a>(<i>toJSON</i>) is <b>true</b></p>
<ol><li><p>
Let
<i>value</i> be the result of calling the [[Call]] internal
method of <i>toJSON </i>passing <i>value</i> as the <b>this</b>
value and with an argument list consisting of <i>key</i>.</p>
</li></ol></li></ol></li>
<li><p>
If
<i>ReplacerFunction</i> is not <b>undefined</b>, then</p>
<ol><li><p>
Let
<i>value</i> be the result of calling the [[Call]] internal method
of <i>ReplacerFunction </i>passing <i>holder</i> as the <b>this</b>
value and with an argument list consisting of <i>key</i> and
<i>value</i>.</p>
</li></ol></li>
<li><p>
If
<a href="x8.html#Type">Type</a>(<i>value</i>) is Object then,</p>
<ol><li><p>
If
the [[Class]] internal property of <i>value</i> is <code><b>"Number"</b></code>
then,</p>
<ol><li><p>
Let
<i>value</i> be <a href="x9.html#x9.3">ToNumber</a>(<i>value</i>).</p>
</li></ol></li>
<li><p>
Else
if the [[Class]] internal property of <i>value</i> is <code><b>"String"</b></code>
then,</p>
<ol><li><p>
Let
<i>value</i> be <a href="x9.html#x9.8">ToString</a>(<i>value</i>).</p>
</li></ol></li>
<li><p>
Else
if the [[Class]] internal property of <i>value</i> is <code><b>"Boolean"</b></code>
then,</p>
<ol><li><p>
Let
<i>value</i> be the value of the [[PrimitiveValue]] internal
property of <i>value</i>.</p>
</li></ol></li></ol></li>
<li><p>
If
<i>value</i> is <b>null</b> then return <code><b>"null"</b></code>.</p>
</li>
<li><p>
If
<i>value</i> is <b>true</b> then return <code><b>"true"</b></code>.</p>
</li>
<li><p>
If
<i>value</i> is <b>false</b> then return <code><b>"false"</b></code>.</p>
</li>
<li><p>
If
<a href="x8.html#Type">Type</a>(<i>value</i>) is String, then return the result of calling the
abstract operation <i><a href="#Quote">Quote</a></i> with argument <i>value</i>.</p>
</li>
<li><p>
If
<a href="x8.html#Type">Type</a>(<i>value</i>) is Number</p>
<ol><li><p>
If
<i>value </i>is finite then return <a href="x9.html#x9.8">ToString</a>(<i>value</i>).</p>
</li>
<li><p>
Else,
return <code><b>"null"</b></code>.</p>
</li></ol></li>
<li><p>
If
<a href="x8.html#Type">Type</a>(<i>value</i>) is Object, and <a href="x9.html#x9.11">IsCallable</a>(<i>value</i>) is <b>false</b></p>
<ol><li><p>
If
the [[Class]] internal property of <i>value</i> is <code><b>"Array"
</b></code>then</p>
<ol><li><p>
Return
the result of calling the abstract operation <i><a href="#JA">JA</a></i> with
argument <i>value</i>.</p>
</li></ol></li>
<li><p>
Else,
return the result of calling the abstract operation <i><a href="#JO">JO</a></i> with
argument <i>value</i>.</p>
</li></ol></li>
<li><p>
Return
<b>undefined</b>.</p>
</li></ol><p>
The
abstract operation <dfn id="Quote"><i>Quote</i>(<i>value</i>)</dfn>
wraps a String value in double quotes and escapes characters within
it.
</p>
<ol><li><p>
Let
<i>product</i> be the double quote character.</p>
</li>
<li><p>
For
each character <i>C</i> in <i>value</i></p>
<ol><li><p>
If
<i>C</i> is the double quote character or the backslash character</p>
<ol><li><p>
Let
<i>product</i> be the concatenation of <i>product</i> and the
backslash character.</p>
</li>
<li><p>
Let
<i>product</i> be the concatenation of <i>product</i> and <i>C</i>.</p>
</li></ol></li>
<li><p>
Else
if <i>C</i> is backspace, formfeed, newline, carriage return, or
tab</p>
<ol><li><p>
Let
<i>product</i> be the concatenation of <i>product</i> and the
backslash character.</p>
</li>
<li><p>
Let
<i>abbrev</i> be the character corresponding to the value of <i>C</i>
as follows:</p>
<p class="pre">backspace <code><b>"b"</b></code></p>
<p class="pre">formfeed <code><b>"f"</b></code></p>
<p class="pre">newline <code><b>"n"</b></code></p>
<p class="pre">carriage return <code><b>"r"</b></code></p>
<p class="pre">tab <code><b>"t"</b></code></p>
</li>
<li><p>
Let
<i>product</i> be the concatenation of <i>product</i> and <i>abbrev</i>.</p>
</li></ol></li>
<li><p>
Else
if <i>C</i> is a control character having a code unit value less
than the space character</p>
<ol><li><p>
Let
<i>product</i> be the concatenation of <i>product</i> and the
backslash character.</p>
</li>
<li><p>
Let
<i>product</i> be the concatenation of <i>product</i> and <code><b>"u"</b></code>.</p>
</li>
<li><p>
Let
<i>hex</i> be the result of converting the numeric code unit
value of <i>C</i> to a String of four hexadecimal digits.</p>
</li>
<li><p>
Let
<i>product</i> be the concatenation of <i>product</i> and <i>hex</i>.</p>
</li></ol></li>
<li><p>
Else</p>
<ol><li><p>
Let
<i>product</i> be the concatenation of <i>product</i> and <i>C</i>.</p>
</li></ol></li></ol></li>
<li><p>
Let
<i>product</i> be the concatenation of <i>product</i> and the
double quote character.</p>
</li>
<li><p>
Return
<i>product</i>.</p>
</li></ol><p>
The
abstract operation <dfn id="JO"><i>JO</i>(<i>value</i>)</dfn>
serializes an object. It has access to the <i>stack</i>,
<i>indent</i>, <i>gap</i>,
<i>PropertyList</i>,
<i>ReplacerFunction</i>,
and <i>space</i> of the
invocation of the stringify method.</p>
<ol><li><p>
If
<i>stack</i> contains <i>value</i> then throw a <b><a href="x15.11.html#x15.11.6.5" class="term-ref">TypeError</a></b>
exception because the structure is cyclical.</p>
</li>
<li><p>
Append
<i>value</i> to <i>stack</i>.</p>
</li>
<li><p>
Let
<i>stepback</i> be <i>indent</i>.</p>
</li>
<li><p>
Let
<i>indent</i> be the concatenation of <i>indent</i> and <i>gap</i>.</p>
</li>
<li><p>
If
<i>PropertyList </i>is not <b>undefined</b>, then</p>
<ol><li><p>
Let
<i>K</i> be <i>PropertyList</i>.</p>
</li></ol></li>
<li><p>
Else</p>
<ol><li><p>
Let
<i>K</i> be an internal <a href="x8.html#x8.8">List</a> of Strings consisting of the names of
all the own properties of <i>value</i> whose [[Enumerable]]
attribute is <b>true</b>. The ordering of the Strings should be
the same as that used by the <b><a href="x15.2.html#x15.2.3.14">Object.keys</a></b> standard built-in
function.</p>
</li></ol></li>
<li><p>
Let
<i>partial</i> be an empty <a href="x8.html#x8.8">List</a>.</p>
</li>
<li><p>
For
each element <i>P</i> of <i>K</i>.</p>
<ol><li><p>
Let
<i>strP</i> be the result of calling the abstract operation <i>Str</i>
with arguments <i>P</i> and <i>value</i>.</p>
</li>
<li><p>
If
<i>strP</i> is not <b>undefined</b></p>
<ol><li><p>
Let
<i>member</i> be the result of calling the abstract operation
<i><a href="#Quote">Quote</a></i> with argument <i>P</i>.</p>
</li>
<li><p>
Let
<i>member</i> be the concatenation of <i>member</i> and the colon
character.</p>
</li>
<li><p>
If
<i>gap</i> is not the empty String</p>
<ol><li><p>
Let
<i>member</i> be the concatenation of <i>member</i> and the
<i>space</i> character.</p>
</li></ol></li>
<li><p>
Let
<i>member</i> be the concatenation of <i>member</i> and <i>strP</i>.</p>
</li>
<li><p>
Append
<i>member</i> to <i>partial</i>.</p>
</li></ol></li></ol></li>
<li><p>
If
<i>partial</i> is empty, then</p>
<ol><li><p>
Let
<i>final</i> be <code><b>"{}"</b></code>.</p>
</li></ol></li>
<li><p>
Else</p>
<ol><li><p>
If
<i>gap</i> is the empty String</p>
<ol><li><p>
Let
<i>properties</i> be a String formed by concatenating all the
element Strings of <i>partial</i> with each adjacent pair of
Strings separated with the comma character. A comma is not
inserted either before the first String or after the last String.
</p>
</li>
<li><p>
Let
<i>final</i> be the result of concatenating <code><b>"{"</b></code><b>,</b>
<i>properties</i>, and <code><b>"}"</b></code>.</p>
</li></ol></li>
<li><p>
Else
<i>gap</i> is not the empty String</p>
<ol><li><p>
Let
<i>separator</i> be the result of concatenating the comma
character, the line feed character, and <i>indent</i>.</p>
</li>
<li><p>
Let
<i>properties</i> be a String formed by concatenating all the
element Strings of <i>partial</i> with each adjacent pair of
Strings separated with <i>separator</i>. The <i>separator</i>
String is not inserted either before the first String or after
the last String.</p>
</li>
<li><p>
Let
<i>final</i> be the result of concatenating <code><b>"{"</b></code>,
the line feed character, <i>indent</i>, <i>properties</i>, the
line feed character, <i>stepback</i>, and <code><b>"}</b></code>".</p>
</li></ol></li></ol></li>
<li><p>
Remove
the last element of <i>stack</i>.</p>
</li>
<li><p>
Let
<i>indent</i> be <i>stepback</i>.</p>
</li>
<li><p>
Return
<i>final</i>.</p>
</li></ol><p>
The
abstract operation <dfn id="JA"><i>JA</i>(<i>value</i>)</dfn>
serializes an array. It has access to the <i>stack</i>,
<i>indent</i>, <i>gap</i>,
and <i>space</i> of the
invocation of the stringify method. The representation of arrays
includes only the elements between zero and <code><b>array.length</b></code>
– 1 inclusive. Named
properties are excluded from the stringification. An array is
stringified as an open left bracket, elements separated by comma,
and a closing right bracket.</p>
<ol><li><p>
If
<i>stack</i> contains <i>value</i> then throw a <b><a href="x15.11.html#x15.11.6.5" class="term-ref">TypeError</a></b>
exception because the structure is cyclical.</p>
</li>
<li><p>
Append
<i>value</i> to <i>stack</i>.</p>
</li>
<li><p>
Let
<i>stepback</i> be <i>indent</i>.</p>
</li>
<li><p>
Let
<i>indent</i> be the concatenation of <i>indent</i> and <i>gap</i>.</p>
</li>
<li><p>
Let
<i>partial</i> be an empty <a href="x8.html#x8.8">List</a>.</p>
</li>
<li><p>
Let
<i>len</i> be the result of calling the [[Get]] internal method of
value with argument <code><b>"length"</b></code>.</p>
</li>
<li><p>
Let
<i>index</i> be 0.</p>
</li>
<li><p>
Repeat
while <i>index</i> < <i>len</i></p>
<ol><li><p>
Let
<i>strP</i> be the result of calling the abstract operation <i>Str</i>
with arguments <a href="x9.html#x9.8">ToString</a>(<i>index</i>) and <i>value</i>.
</p>
</li>
<li><p>
If
<i>strP</i> is <b>undefined</b></p>
<ol><li><p>
Append
<code><b>"null"</b></code>
to <i>partial</i>.</p>
</li></ol></li>
<li><p>
Else</p>
<ol><li><p>
Append
<i>strP</i> to <i>partial</i>.</p>
</li></ol></li>
<li><p>
Increment
<i>index</i> by 1.</p>
</li></ol></li>
<li><p>
If
<i>partial</i> is empty ,then</p>
<ol><li><p>
Let
<i>final</i> be <code><b>"[]"</b></code>.</p>
</li></ol></li>
<li><p>
Else</p>
<ol><li><p>
If
<i>gap</i> is the empty String</p>
<ol><li><p>
Let
<i>properties</i> be a String formed by concatenating all the
element Strings of <i>partial</i> with each adjacent pair of
Strings separated with the comma character. A comma is not
inserted either before the first String or after the last String.
</p>
</li>
<li><p>
Let
<i>final</i> be the result of concatenating <code><b>"["</b></code><b>,</b>
<i>properties</i>, and <code><b>"]"</b></code>.</p>
</li></ol></li>
<li><p>
Else</p>
<ol><li><p>
Let
<i>separator</i> be the result of concatenating the comma
character, the line feed character, and <i>indent</i>.</p>
</li>
<li><p>
Let
<i>properties</i> be a String formed by concatenating all the
element Strings of <i>partial</i> with each adjacent pair of
Strings separated with <i>separator</i>. The <i>separator</i>
String is not inserted either before the first String or after
the last String.</p>
</li>
<li><p>
Let
<i>final</i> be the result of concatenating "<code><b>[</b></code>",
the line feed character, <i>indent</i>, <i>properties</i>, the
line feed character, <i>stepback</i>, and "<code><b>]</b></code>".</p>
</li></ol></li></ol></li>
<li><p>
Remove
the last element of <i>stack</i>.</p>
</li>
<li><p>
Let
<i>indent</i> be <i>stepback</i>.</p>
</li>
<li><p>
Return
<i>final</i>.</p>
</li></ol><p><b class="note">NOTE 1</b> JSON structures are allowed to be nested to any depth, but they
must be acyclic. If <i>value</i>
is or contains a cyclic structure, then the stringify function must
throw a <b><a href="x15.11.html#x15.11.6.5" class="term-ref">TypeError</a></b> exception. This is an example of a value
that cannot be stringified:</p>
<p class="code-example"><code><b>a = [];</b></code></p>
<p class="code-example"><code><b>a[0] = a;</b></code></p>
<p class="code-example"><code><b>my_text = JSON.stringify(a); // This must throw an TypeError.</b></code></p>
<br><p><b class="note">NOTE 2</b> Symbolic <a href="x4.html#primitive_value" class="term-ref">primitive value</a>s are rendered as follows:</p>
<ul><li><p>The
<b>null</b> value is rendered in JSON text as the String <code>null</code>.</p>
</li>
<li><p>The
<b>undefined</b> value is not rendered.</p>
</li>
<li><p>The
<b>true</b> value is rendered in JSON text as the String <code>true</code>.</p>
</li>
<li><p class="sp">The
<b>false</b> value is rendered in JSON text as the String <code>false</code>.</p>
</li></ul><p class="sp"><b class="note">NOTE 3</b> String values are wrapped in double quotes. The characters <code><b>"</b></code>
and <code><b>\</b></code> are escaped
with <code><b>\</b></code> prefixes.
Control characters are replaced with escape sequences <code><b>\u</b></code>HHHH,
or with the shorter forms, <code><b>\b</b></code>