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<li><span class="stability_1"><a href="#modules-typescript">Modules: TypeScript</a></span>
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<details role="navigation" id="toc" open><summary>Table of contents</summary><ul>
<li><span class="stability_1"><a href="#modules-typescript">Modules: TypeScript</a></span>
<ul>
<li><a href="#enabling">Enabling</a></li>
<li><a href="#full-typescript-support">Full TypeScript support</a></li>
<li><span class="stability_1"><a href="#type-stripping">Type stripping</a></span>
<ul>
<li><a href="#determining-module-system">Determining module system</a></li>
<li><a href="#typescript-features">TypeScript features</a></li>
<li><a href="#importing-types-without-type-keyword">Importing types without <code>type</code> keyword</a></li>
<li><a href="#non-file-forms-of-input">Non-file forms of input</a></li>
<li><a href="#source-maps">Source maps</a></li>
<li><a href="#type-stripping-in-dependencies">Type stripping in dependencies</a></li>
<li><a href="#paths-aliases">Paths aliases</a></li>
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<div role="main" id="apicontent">
<h2>Modules: TypeScript<span><a class="mark" href="#modules-typescript" id="modules-typescript">#</a></span><a aria-hidden="true" class="legacy" id="typescript_modules_typescript"></a></h2>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tbody><tr><th>Version</th><th>Changes</th></tr>
<tr><td>v22.7.0</td>
<td><p>Added <code>--experimental-transform-types</code> flag.</p></td></tr>
</tbody></table>
</details>
</div>
<p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a>.1 - Active development</div><p></p>
<section><h3>Enabling<span><a class="mark" href="#enabling" id="enabling">#</a></span><a aria-hidden="true" class="legacy" id="typescript_enabling"></a></h3>
<p>There are two ways to enable runtime TypeScript support in Node.js:</p>
<ol>
<li>
<p>For <a href="#full-typescript-support">full support</a> of all of TypeScript's syntax and features, including
using any version of TypeScript, use a third-party package.</p>
</li>
<li>
<p>For lightweight support, you can use the built-in support for
<a href="#type-stripping">type stripping</a>.</p>
</li>
</ol>
</section><section><h3>Full TypeScript support<span><a class="mark" href="#full-typescript-support" id="full-typescript-support">#</a></span><a aria-hidden="true" class="legacy" id="typescript_full_typescript_support"></a></h3>
<p>To use TypeScript with full support for all TypeScript features, including
<code>tsconfig.json</code>, you can use a third-party package. These instructions use
<a href="https://tsx.is/"><code>tsx</code></a> as an example but there are many other similar libraries available.</p>
<ol>
<li>
<p>Install the package as a development dependency using whatever package
manager you're using for your project. For example, with <code>npm</code>:</p>
<pre><code class="language-bash">npm install --save-dev tsx</code> <button class="copy-button">copy</button></pre>
</li>
<li>
<p>Then you can run your TypeScript code via:</p>
<pre><code class="language-bash">npx tsx your-file.ts</code> <button class="copy-button">copy</button></pre>
<p>Or alternatively, you can run with <code>node</code> via:</p>
<pre><code class="language-bash">node --import=tsx your-file.ts</code> <button class="copy-button">copy</button></pre>
</li>
</ol>
</section><section><h3>Type stripping<span><a class="mark" href="#type-stripping" id="type-stripping">#</a></span><a aria-hidden="true" class="legacy" id="typescript_type_stripping"></a></h3>
<div class="api_metadata">
<span>Added in: v22.6.0</span>
</div>
<p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a>.1 - Active development</div><p></p>
<p>The flag <a href="cli.html#--experimental-strip-types"><code>--experimental-strip-types</code></a> enables Node.js to run TypeScript
files. By default Node.js will execute only files that contain no
TypeScript features that require transformation, such as enums or namespaces.
Node.js will replace inline type annotations with whitespace,
and no type checking is performed.
To enable the transformation of such features
use the flag <a href="cli.html#--experimental-transform-types"><code>--experimental-transform-types</code></a>.
TypeScript features that depend on settings within <code>tsconfig.json</code>,
such as paths or converting newer JavaScript syntax to older standards, are
intentionally unsupported. To get full TypeScript support, see <a href="#full-typescript-support">Full TypeScript support</a>.</p>
<p>The type stripping feature is designed to be lightweight.
By intentionally not supporting syntaxes that require JavaScript code
generation, and by replacing inline types with whitespace, Node.js can run
TypeScript code without the need for source maps.</p>
<p>Type stripping works with most versions of TypeScript
but we recommend version 5.7 or newer with the following <code>tsconfig.json</code> settings:</p>
<pre><code class="language-json"><span class="hljs-punctuation">{</span>
<span class="hljs-attr">"compilerOptions"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">{</span>
<span class="hljs-attr">"target"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"esnext"</span><span class="hljs-punctuation">,</span>
<span class="hljs-attr">"module"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"nodenext"</span><span class="hljs-punctuation">,</span>
<span class="hljs-attr">"allowImportingTsExtensions"</span><span class="hljs-punctuation">:</span> <span class="hljs-literal"><span class="hljs-keyword">true</span></span><span class="hljs-punctuation">,</span>
<span class="hljs-attr">"rewriteRelativeImportExtensions"</span><span class="hljs-punctuation">:</span> <span class="hljs-literal"><span class="hljs-keyword">true</span></span><span class="hljs-punctuation">,</span>
<span class="hljs-attr">"verbatimModuleSyntax"</span><span class="hljs-punctuation">:</span> <span class="hljs-literal"><span class="hljs-keyword">true</span></span>
<span class="hljs-punctuation">}</span>
<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre>
<h4>Determining module system<span><a class="mark" href="#determining-module-system" id="determining-module-system">#</a></span><a aria-hidden="true" class="legacy" id="typescript_determining_module_system"></a></h4>
<p>Node.js supports both <a href="modules.html">CommonJS</a> and <a href="esm.html">ES Modules</a> syntax in TypeScript
files. Node.js will not convert from one module system to another; if you want
your code to run as an ES module, you must use <code>import</code> and <code>export</code> syntax, and
if you want your code to run as CommonJS you must use <code>require</code> and
<code>module.exports</code>.</p>
<ul>
<li><code>.ts</code> files will have their module system determined <a href="packages.html#determining-module-system">the same way as <code>.js</code>
files.</a> To use <code>import</code> and <code>export</code> syntax, add <code>"type": "module"</code> to the
nearest parent <code>package.json</code>.</li>
<li><code>.mts</code> files will always be run as ES modules, similar to <code>.mjs</code> files.</li>
<li><code>.cts</code> files will always be run as CommonJS modules, similar to <code>.cjs</code> files.</li>
<li><code>.tsx</code> files are unsupported.</li>
</ul>
<p>As in JavaScript files, <a href="esm.html#mandatory-file-extensions">file extensions are mandatory</a> in <code>import</code> statements
and <code>import()</code> expressions: <code>import './file.ts'</code>, not <code>import './file'</code>. Because
of backward compatibility, file extensions are also mandatory in <code>require()</code>
calls: <code>require('./file.ts')</code>, not <code>require('./file')</code>, similar to how the
<code>.cjs</code> extension is mandatory in <code>require</code> calls in CommonJS files.</p>
<p>The <code>tsconfig.json</code> option <code>allowImportingTsExtensions</code> will allow the
TypeScript compiler <code>tsc</code> to type-check files with <code>import</code> specifiers that
include the <code>.ts</code> extension.</p>
<h4>TypeScript features<span><a class="mark" href="#typescript-features" id="typescript-features">#</a></span><a aria-hidden="true" class="legacy" id="typescript_typescript_features"></a></h4>
<p>Since Node.js is only removing inline types, any TypeScript features that
involve <em>replacing</em> TypeScript syntax with new JavaScript syntax will error,
unless the flag <a href="cli.html#--experimental-transform-types"><code>--experimental-transform-types</code></a> is passed.</p>
<p>The most prominent features that require transformation are:</p>
<ul>
<li><code>Enum</code></li>
<li><code>namespaces</code></li>
<li><code>legacy module</code></li>
<li>parameter properties</li>
</ul>
<p>Since Decorators are currently a <a href="https://github.com/tc39/proposal-decorators">TC39 Stage 3 proposal</a>
and will soon be supported by the JavaScript engine,
they are not transformed and will result in a parser error.
This is a temporary limitation and will be resolved in the future.</p>
<p>In addition, Node.js does not read <code>tsconfig.json</code> files and does not support
features that depend on settings within <code>tsconfig.json</code>, such as paths or
converting newer JavaScript syntax into older standards.</p>
<h4>Importing types without <code>type</code> keyword<span><a class="mark" href="#importing-types-without-type-keyword" id="importing-types-without-type-keyword">#</a></span><a aria-hidden="true" class="legacy" id="typescript_importing_types_without_type_keyword"></a></h4>
<p>Due to the nature of type stripping, the <code>type</code> keyword is necessary to
correctly strip type imports. Without the <code>type</code> keyword, Node.js will treat the
import as a value import, which will result in a runtime error. The tsconfig
option <a href="https://www.typescriptlang.org/tsconfig/#verbatimModuleSyntax"><code>verbatimModuleSyntax</code></a> can be used to match this behavior.</p>
<p>This example will work correctly:</p>
<pre><code class="language-ts"><span class="hljs-keyword">import</span> <span class="hljs-keyword">type</span> { <span class="hljs-title class_">Type1</span>, <span class="hljs-title class_">Type2</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'./module.ts'</span>;
<span class="hljs-keyword">import</span> { fn, <span class="hljs-keyword">type</span> <span class="hljs-title class_">FnParams</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'./fn.ts'</span>;</code> <button class="copy-button">copy</button></pre>
<p>This will result in a runtime error:</p>
<pre><code class="language-ts"><span class="hljs-keyword">import</span> { <span class="hljs-title class_">Type1</span>, <span class="hljs-title class_">Type2</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'./module.ts'</span>;
<span class="hljs-keyword">import</span> { fn, <span class="hljs-title class_">FnParams</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'./fn.ts'</span>;</code> <button class="copy-button">copy</button></pre>
<h4>Non-file forms of input<span><a class="mark" href="#non-file-forms-of-input" id="non-file-forms-of-input">#</a></span><a aria-hidden="true" class="legacy" id="typescript_non_file_forms_of_input"></a></h4>
<p>Type stripping can be enabled for <code>--eval</code>. The module system
will be determined by <code>--input-type</code>, as it is for JavaScript.</p>
<p>TypeScript syntax is unsupported in the REPL, STDIN input, <code>--print</code>, <code>--check</code>, and
<code>inspect</code>.</p>
<h4>Source maps<span><a class="mark" href="#source-maps" id="source-maps">#</a></span><a aria-hidden="true" class="legacy" id="typescript_source_maps"></a></h4>
<p>Since inline types are replaced by whitespace, source maps are unnecessary for
correct line numbers in stack traces; and Node.js does not generate them.
When <a href="cli.html#--experimental-transform-types"><code>--experimental-transform-types</code></a> is enabled, source-maps
are enabled by default.</p>
<h4>Type stripping in dependencies<span><a class="mark" href="#type-stripping-in-dependencies" id="type-stripping-in-dependencies">#</a></span><a aria-hidden="true" class="legacy" id="typescript_type_stripping_in_dependencies"></a></h4>
<p>To discourage package authors from publishing packages written in TypeScript,
Node.js will by default refuse to handle TypeScript files inside folders under
a <code>node_modules</code> path.</p>
<h4>Paths aliases<span><a class="mark" href="#paths-aliases" id="paths-aliases">#</a></span><a aria-hidden="true" class="legacy" id="typescript_paths_aliases"></a></h4>
<p><a href="https://www.typescriptlang.org/tsconfig/#paths"><code>tsconfig</code> "paths"</a> won't be transformed and therefore produce an error. The closest
feature available is <a href="packages.html#subpath-imports">subpath imports</a> with the limitation that they need to start
with <code>#</code>.</p></section>
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