Revision 766243 of JSON

<div>{{JSRef("Global_Objects", "JSON")}}</div>

<h2 id="Summary" name="Summary">Summary</h2>

<p>The <strong><code>JSON</code></strong> object contains methods for parsing <a class="external" href="https://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" name="Description">Description</h2>

<h3 id="JavaScript_Object_Notation" name="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="https://timelessrepo.com/json-isnt-a-javascript-subset">JSON: The JavaScript subset that isn't</a>.</p>

<table align="left">
 <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="https://unicode-table.com/en/2028/">U+2028</a>) and paragraph separator (<a href="https://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="https://unicode-table.com/en/0009/">U+0009</a>), carriage return (<a href="https://unicode-table.com/en/000D/">U+000D</a>), line feed (<a href="https://unicode-table.com/en/000A/">U+000A</a>), and space (<a href="https://unicode-table.com/en/0020/">U+0020</a>) characters are the only valid whitespace characters.</p>

<h2 id="Methods" name="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" name="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(vContent) {
      if (vContent instanceof Object) {
        var sOutput = '';
        if (vContent.constructor === Array) {
          for (var nId = 0; nId &lt; vContent.length; sOutput += this.stringify(vContent[nId]) + ',', nId++);
          return '[' + sOutput.substr(0, sOutput.length - 1) + ']';
        }
        if (vContent.toString !== Object.prototype.toString) {
          return '"' + vContent.toString().replace(/"/g, '\\$&amp;') + '"';
        }
        for (var sProp in vContent) {
          sOutput += '"' + sProp.replace(/"/g, '\\$&amp;') + '":' + this.stringify(vContent[sProp]) + ',';
        }
        return '{' + sOutput.substr(0, sOutput.length - 1) + '}';
     }
     return typeof vContent === 'string' ? '"' + vContent.replace(/"/g, '\\$&amp;') + '"' : String(vContent);
    }
  };
}
</pre>

<p>More complex well-known <a class="external" href="https://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="https://bestiejs.github.com/json3">JSON3</a>.</p>

<h2 id="Specifications" name="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>&nbsp;</td>
  </tr>
  <tr>
   <td>{{SpecName('ES6', '#sec-json-object', 'JSON')}}</td>
   <td>{{Spec2('ES6')}}</td>
   <td>&nbsp;</td>
  </tr>
 </tbody>
</table>

<h2 id="Browser_compatibility" name="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>

<p>Based on <a class="external" href="https://kangax.github.com/es5-compat-table/">Kangax's compat table</a>.</p>

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

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