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<li><span class="stability_2"><a href="#string-decoder">String decoder</a></span>
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<li><a href="#class-stringdecoder">Class: <code>StringDecoder</code></a>
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<li><a href="#new-stringdecoderencoding"><code>new StringDecoder([encoding])</code></a></li>
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<details role="navigation" id="toc" open><summary>Table of contents</summary><ul>
<li><span class="stability_2"><a href="#string-decoder">String decoder</a></span>
<ul>
<li><a href="#class-stringdecoder">Class: <code>StringDecoder</code></a>
<ul>
<li><a href="#new-stringdecoderencoding"><code>new StringDecoder([encoding])</code></a></li>
<li><a href="#stringdecoderendbuffer"><code>stringDecoder.end([buffer])</code></a></li>
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<h2>String decoder<span><a class="mark" href="#string-decoder" id="string-decoder">#</a></span><a aria-hidden="true" class="legacy" id="string_decoder_string_decoder"></a></h2>
<p></p><div class="api_stability api_stability_2"><a href="documentation.html#stability-index">Stability: 2</a> - Stable</div><p></p>
<p><strong>Source Code:</strong> <a href="https://github.com/nodejs/node/blob/v22.14.0/lib/string_decoder.js">lib/string_decoder.js</a></p>
<p>The <code>node:string_decoder</code> module provides an API for decoding <code>Buffer</code> objects
into strings in a manner that preserves encoded multi-byte UTF-8 and UTF-16
characters. It can be accessed using:</p>
<pre class="with-57-chars"><input class="js-flavor-toggle" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { <span class="hljs-title class_">StringDecoder</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:string_decoder'</span>;</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { <span class="hljs-title class_">StringDecoder</span> } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:string_decoder'</span>);</code><button class="copy-button">copy</button></pre>
<p>The following example shows the basic use of the <code>StringDecoder</code> class.</p>
<pre class="with-57-chars"><input class="js-flavor-toggle" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { <span class="hljs-title class_">StringDecoder</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:string_decoder'</span>;
<span class="hljs-keyword">import</span> { <span class="hljs-title class_">Buffer</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:buffer'</span>;
<span class="hljs-keyword">const</span> decoder = <span class="hljs-keyword">new</span> <span class="hljs-title class_">StringDecoder</span>(<span class="hljs-string">'utf8'</span>);
<span class="hljs-keyword">const</span> cent = <span class="hljs-title class_">Buffer</span>.<span class="hljs-title function_">from</span>([<span class="hljs-number">0xC2</span>, <span class="hljs-number">0xA2</span>]);
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(decoder.<span class="hljs-title function_">write</span>(cent)); <span class="hljs-comment">// Prints: ¢</span>
<span class="hljs-keyword">const</span> euro = <span class="hljs-title class_">Buffer</span>.<span class="hljs-title function_">from</span>([<span class="hljs-number">0xE2</span>, <span class="hljs-number">0x82</span>, <span class="hljs-number">0xAC</span>]);
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(decoder.<span class="hljs-title function_">write</span>(euro)); <span class="hljs-comment">// Prints: €</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> { <span class="hljs-title class_">StringDecoder</span> } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:string_decoder'</span>);
<span class="hljs-keyword">const</span> decoder = <span class="hljs-keyword">new</span> <span class="hljs-title class_">StringDecoder</span>(<span class="hljs-string">'utf8'</span>);
<span class="hljs-keyword">const</span> cent = <span class="hljs-title class_">Buffer</span>.<span class="hljs-title function_">from</span>([<span class="hljs-number">0xC2</span>, <span class="hljs-number">0xA2</span>]);
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(decoder.<span class="hljs-title function_">write</span>(cent)); <span class="hljs-comment">// Prints: ¢</span>
<span class="hljs-keyword">const</span> euro = <span class="hljs-title class_">Buffer</span>.<span class="hljs-title function_">from</span>([<span class="hljs-number">0xE2</span>, <span class="hljs-number">0x82</span>, <span class="hljs-number">0xAC</span>]);
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(decoder.<span class="hljs-title function_">write</span>(euro)); <span class="hljs-comment">// Prints: €</span></code><button class="copy-button">copy</button></pre>
<p>When a <code>Buffer</code> instance is written to the <code>StringDecoder</code> instance, an
internal buffer is used to ensure that the decoded string does not contain
any incomplete multibyte characters. These are held in the buffer until the
next call to <code>stringDecoder.write()</code> or until <code>stringDecoder.end()</code> is called.</p>
<p>In the following example, the three UTF-8 encoded bytes of the European Euro
symbol (<code>€</code>) are written over three separate operations:</p>
<pre class="with-57-chars"><input class="js-flavor-toggle" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { <span class="hljs-title class_">StringDecoder</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:string_decoder'</span>;
<span class="hljs-keyword">import</span> { <span class="hljs-title class_">Buffer</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:buffer'</span>;
<span class="hljs-keyword">const</span> decoder = <span class="hljs-keyword">new</span> <span class="hljs-title class_">StringDecoder</span>(<span class="hljs-string">'utf8'</span>);
decoder.<span class="hljs-title function_">write</span>(<span class="hljs-title class_">Buffer</span>.<span class="hljs-title function_">from</span>([<span class="hljs-number">0xE2</span>]));
decoder.<span class="hljs-title function_">write</span>(<span class="hljs-title class_">Buffer</span>.<span class="hljs-title function_">from</span>([<span class="hljs-number">0x82</span>]));
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(decoder.<span class="hljs-title function_">end</span>(<span class="hljs-title class_">Buffer</span>.<span class="hljs-title function_">from</span>([<span class="hljs-number">0xAC</span>]))); <span class="hljs-comment">// Prints: €</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> { <span class="hljs-title class_">StringDecoder</span> } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:string_decoder'</span>);
<span class="hljs-keyword">const</span> decoder = <span class="hljs-keyword">new</span> <span class="hljs-title class_">StringDecoder</span>(<span class="hljs-string">'utf8'</span>);
decoder.<span class="hljs-title function_">write</span>(<span class="hljs-title class_">Buffer</span>.<span class="hljs-title function_">from</span>([<span class="hljs-number">0xE2</span>]));
decoder.<span class="hljs-title function_">write</span>(<span class="hljs-title class_">Buffer</span>.<span class="hljs-title function_">from</span>([<span class="hljs-number">0x82</span>]));
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(decoder.<span class="hljs-title function_">end</span>(<span class="hljs-title class_">Buffer</span>.<span class="hljs-title function_">from</span>([<span class="hljs-number">0xAC</span>]))); <span class="hljs-comment">// Prints: €</span></code><button class="copy-button">copy</button></pre>
<section><h3>Class: <code>StringDecoder</code><span><a class="mark" href="#class-stringdecoder" id="class-stringdecoder">#</a></span><a aria-hidden="true" class="legacy" id="string_decoder_class_stringdecoder"></a></h3>
<h4><code>new StringDecoder([encoding])</code><span><a class="mark" href="#new-stringdecoderencoding" id="new-stringdecoderencoding">#</a></span><a aria-hidden="true" class="legacy" id="string_decoder_new_stringdecoder_encoding"></a></h4>
<div class="api_metadata">
<span>Added in: v0.1.99</span>
</div>
<ul>
<li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The character <a href="buffer.html#buffers-and-character-encodings">encoding</a> the <code>StringDecoder</code> will use.
<strong>Default:</strong> <code>'utf8'</code>.</li>
</ul>
<p>Creates a new <code>StringDecoder</code> instance.</p>
<h4><code>stringDecoder.end([buffer])</code><span><a class="mark" href="#stringdecoderendbuffer" id="stringdecoderendbuffer">#</a></span><a aria-hidden="true" class="legacy" id="string_decoder_stringdecoder_end_buffer"></a></h4>
<div class="api_metadata">
<span>Added in: v0.9.3</span>
</div>
<ul>
<li><code>buffer</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="buffer.html#class-buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a> The bytes to decode.</li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
</ul>
<p>Returns any remaining input stored in the internal buffer as a string. Bytes
representing incomplete UTF-8 and UTF-16 characters will be replaced with
substitution characters appropriate for the character encoding.</p>
<p>If the <code>buffer</code> argument is provided, one final call to <code>stringDecoder.write()</code>
is performed before returning the remaining input.
After <code>end()</code> is called, the <code>stringDecoder</code> object can be reused for new input.</p>
<h4><code>stringDecoder.write(buffer)</code><span><a class="mark" href="#stringdecoderwritebuffer" id="stringdecoderwritebuffer">#</a></span><a aria-hidden="true" class="legacy" id="string_decoder_stringdecoder_write_buffer"></a></h4>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tbody><tr><th>Version</th><th>Changes</th></tr>
<tr><td>v8.0.0</td>
<td><p>Each invalid character is now replaced by a single replacement character instead of one for each individual byte.</p></td></tr>
<tr><td>v0.1.99</td>
<td><p><span>Added in: v0.1.99</span></p></td></tr>
</tbody></table>
</details>
</div>
<ul>
<li><code>buffer</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="buffer.html#class-buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a> The bytes to decode.</li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
</ul>
<p>Returns a decoded string, ensuring that any incomplete multibyte characters at
the end of the <code>Buffer</code>, or <code>TypedArray</code>, or <code>DataView</code> are omitted from the
returned string and stored in an internal buffer for the next call to
<code>stringDecoder.write()</code> or <code>stringDecoder.end()</code>.</p></section>
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