path: root/files/it/web/javascript/reference/global_objects/json/index.html

---
title: JSON
slug: Web/JavaScript/Reference/Global_Objects/JSON
tags:
  - JSON
  - JavaScript
  - NeedsTranslation
  - Object
  - Reference
  - TopicStub
  - polyfill
translation_of: Web/JavaScript/Reference/Global_Objects/JSON
---
<div>{{JSRef}}</div>

<p>The <strong><code>JSON</code></strong> object contains methods for parsing <a class="external" href="http://json.org/">JavaScript Object Notation</a> ({{glossary("JSON")}}) and converting values to JSON. It can't be called or constructed, and aside from its two method properties it has no interesting functionality of its own.</p>

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

<h3 id="JavaScript_Object_Notation">JavaScript Object Notation</h3>

<p>JSON is a syntax for serializing objects, arrays, numbers, strings, booleans, and {{jsxref("null")}}. It is based upon JavaScript syntax but is distinct from it: some JavaScript is not JSON, and some JSON is not JavaScript. See also <a href="http://timelessrepo.com/json-isnt-a-javascript-subset">JSON: The JavaScript subset that isn't</a>.</p>

<table>
 <caption>JavaScript and JSON differences</caption>
 <thead>
  <tr>
   <th scope="col">JavaScript type</th>
   <th scope="col">JSON differences</th>
  </tr>
 </thead>
 <tbody>
  <tr>
   <td>Objects and Arrays</td>
   <td>Property names must be double-quoted strings; trailing commas are forbidden.</td>
  </tr>
  <tr>
   <td>Numbers</td>
   <td>Leading zeros are prohibited; a decimal point must be followed by at least one digit.</td>
  </tr>
  <tr>
   <td>Strings</td>
   <td>
    <p>Only a limited sets of characters may be escaped; certain control characters are prohibited; the Unicode line separator (<a href="http://unicode-table.com/en/2028/">U+2028</a>) and paragraph separator (<a href="http://unicode-table.com/en/2029/">U+2029</a>) characters are permitted; strings must be double-quoted. See the following example where {{jsxref("JSON.parse()")}} works fine and a {{jsxref("SyntaxError")}} is thrown when evaluating the code as JavaScript:</p>

    <pre class="brush: js">
var code = '"\u2028\u2029"';
JSON.parse(code); // works fine
eval(code); // fails
</pre>
   </td>
  </tr>
 </tbody>
</table>

<p>The full JSON syntax is as follows:</p>

<pre><var>JSON</var> = <strong>null</strong>
    <em>or</em> <strong>true</strong> <em>or</em> <strong>false</strong>
    <em>or</em> <var>JSONNumber</var>
    <em>or</em> <var>JSONString</var>
    <em>or</em> <var>JSONObject</var>
    <em>or</em> <var>JSONArray</var>

<var>JSONNumber</var> = <strong>-</strong> <var>PositiveNumber</var>
          <em>or</em> <var>PositiveNumber</var>
<var>PositiveNumber</var> = DecimalNumber
              <em>or</em> <var>DecimalNumber</var> <strong>.</strong> <var>Digits</var>
              <em>or</em> <var>DecimalNumber</var> <strong>.</strong> <var>Digits</var> <var>ExponentPart</var>
              <em>or</em> <var>DecimalNumber</var> <var>ExponentPart</var>
<var>DecimalNumber</var> = <strong>0</strong>
             <em>or</em> <var>OneToNine</var> <var>Digits</var>
<var>ExponentPart</var> = <strong>e</strong> <var>Exponent</var>
            <em>or</em> <strong>E</strong> <var>Exponent</var>
<var>Exponent</var> = <var>Digits</var>
        <em>or</em> <strong>+</strong> <var>Digits</var>
        <em>or</em> <strong>-</strong> <var>Digits</var>
<var>Digits</var> = <var>Digit</var>
      <em>or</em> <var>Digits</var> <var>Digit</var>
<var>Digit</var> = <strong>0</strong> through <strong>9</strong>
<var>OneToNine</var> = <strong>1</strong> through <strong>9</strong>

<var>JSONString</var> = <strong>""</strong>
          <em>or</em> <strong>"</strong> <var>StringCharacters</var> <strong>"</strong>
<var>StringCharacters</var> = <var>StringCharacter</var>
                <em>or</em> <var>StringCharacters</var> <var>StringCharacter</var>
<var>StringCharacter</var> = any character
                  <em>except</em> <strong>"</strong> <em>or</em> <strong>\</strong> <em>or</em> U+0000 through U+001F
               <em>or</em> <var>EscapeSequence</var>
<var>EscapeSequence</var> = <strong>\"</strong> <em>or</em> <strong>\/</strong> <em>or</em> <strong>\\</strong> <em>or</em> <strong>\b</strong> <em>or</em> <strong>\f</strong> <em>or</em> <strong>\n</strong> <em>or</em> <strong>\r</strong> <em>or</em> <strong>\t</strong>
              <em>or</em> <strong>\u</strong> <var>HexDigit</var> <var>HexDigit</var> <var>HexDigit</var> <var>HexDigit</var>
<var>HexDigit</var> = <strong>0</strong> through <strong>9</strong>
        <em>or</em> <strong>A</strong> through <strong>F</strong>
        <em>or</em> <strong>a</strong> through <strong>f</strong>

<var>JSONObject</var> = <strong>{</strong> <strong>}</strong>
          <em>or</em> <strong>{</strong> <var>Members</var> <strong>}</strong>
<var>Members</var> = <var>JSONString</var> <strong>:</strong> <var>JSON</var>
       <em>or</em> <var>Members</var> <strong>,</strong> <var>JSONString</var> <strong>:</strong> <var>JSON</var>

<var>JSONArray</var> = <strong>[</strong> <strong>]</strong>
         <em>or</em> <strong>[</strong> <var>ArrayElements</var> <strong>]</strong>
<var>ArrayElements</var> = <var>JSON</var>
             <em>or</em> <var>ArrayElements</var> <strong>,</strong> <var>JSON</var>
</pre>

<p>Insignificant whitespace may be present anywhere except within a <code><var>JSONNumber</var></code> (numbers must contain no whitespace) or <code><var>JSONString</var></code> (where it is interpreted as the corresponding character in the string, or would cause an error). The tab character (<a href="http://unicode-table.com/en/0009/">U+0009</a>), carriage return (<a href="http://unicode-table.com/en/000D/">U+000D</a>), line feed (<a href="http://unicode-table.com/en/000A/">U+000A</a>), and space (<a href="http://unicode-table.com/en/0020/">U+0020</a>) characters are the only valid whitespace characters.</p>

<h2 id="Methods">Methods</h2>

<dl>
 <dt>{{jsxref("JSON.parse()")}}</dt>
 <dd>Parse a string as JSON, optionally transform the produced value and its properties, and return the value.</dd>
 <dt>{{jsxref("JSON.stringify()")}}</dt>
 <dd>Return a JSON string corresponding to the specified value, optionally including only certain properties or replacing property values in a user-defined manner.</dd>
</dl>

<h2 id="Polyfill">Polyfill</h2>

<p>The <code>JSON</code> object is not supported in older browsers. You can work around this by inserting the following code at the beginning of your scripts, allowing use of <code>JSON</code> object in implementations which do not natively support it (like Internet Explorer 6).</p>

<p>The following algorithm is an imitation of the native <code>JSON</code> object:</p>

<pre class="brush: js">if (!window.JSON) {
  window.JSON = {
    parse: function(sJSON) { return eval('(' + sJSON + ')'); },
    stringify: (function () {
      var toString = Object.prototype.toString;
      var isArray = Array.isArray || function (a) { return toString.call(a) === '[object Array]'; };
      var escMap = {'"': '\\"', '\\': '\\\\', '\b': '\\b', '\f': '\\f', '\n': '\\n', '\r': '\\r', '\t': '\\t'};
      var escFunc = function (m) { return escMap[m] || '\\u' + (m.charCodeAt(0) + 0x10000).toString(16).substr(1); };
      var escRE = /[\\"\u0000-\u001F\u2028\u2029]/g;
      return function stringify(value) {
        if (value == null) {
          return 'null';
        } else if (typeof value === 'number') {
          return isFinite(value) ? value.toString() : 'null';
        } else if (typeof value === 'boolean') {
          return value.toString();
        } else if (typeof value === 'object') {
          if (typeof value.toJSON === 'function') {
            return stringify(value.toJSON());
          } else if (isArray(value)) {
            var res = '[';
            for (var i = 0; i &lt; value.length; i++)
              res += (i ? ', ' : '') + stringify(value[i]);
            return res + ']';
          } else if (toString.call(value) === '[object Object]') {
            var tmp = [];
            for (var k in value) {
              if (value.hasOwnProperty(k))
                tmp.push(stringify(k) + ': ' + stringify(value[k]));
            }
            return '{' + tmp.join(', ') + '}';
          }
        }
        return '"' + value.toString().replace(escRE, escFunc) + '"';
      };
    })()
  };
}
</pre>

<p>More complex well-known <a class="external" href="http://remysharp.com/2010/10/08/what-is-a-polyfill/">polyfills</a> for the <code>JSON</code> object are <a class="link-https" href="https://github.com/douglascrockford/JSON-js">JSON2</a> and <a class="external" href="http://bestiejs.github.com/json3">JSON3</a>.</p>

<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('ES5.1', '#sec-15.12', 'JSON')}}</td>
   <td>{{Spec2('ES5.1')}}</td>
   <td> </td>
  </tr>
  <tr>
   <td>{{SpecName('ES6', '#sec-json-object', 'JSON')}}</td>
   <td>{{Spec2('ES6')}}</td>
   <td> </td>
  </tr>
 </tbody>
</table>

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

<div>{{CompatibilityTable}}</div>

<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>{{CompatGeckoDesktop("1.9.1")}}</td>
   <td>{{CompatIE("8.0")}}</td>
   <td>{{CompatOpera("10.5")}}</td>
   <td>{{CompatSafari("4.0")}}</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>{{CompatGeckoMobile("1.0")}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

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

<ul>
 <li>{{jsxref("Date.prototype.toJSON()")}}</li>
</ul>