<p>During the last two years, ESM support in TypeScript, Node.js and browsers has made a lot of progress. In this blog post, I explain my modern setup that is relatively simple – compared to what we had to do in the past:</p><ul><li>It is intended for packages that can afford to ignore backward compatibility. The setup has worked well for me for a while – since TypeScript 4.7 (2022-05-24).<ul><li>It helps that Node.js now supports <a href="https://nodejs.org/api/modules.html#loading-ecmascript-modules-using-require">“require(esm)”</a> – requiring ESM libraries from CommonJS modules.</li></ul></li><li>I’m only using tsc, but mention how to support other tools via <code>tsconfig.json</code> in section <a href="#compiling-without-tsc">“Compiling TypeScript with tools other than tsc”</a>.</li></ul>

<p>JavaScript’s Arrays are so flexible that TypeScript provides two different kinds of types for handling them:</p><ul><li>Array types for arbitrary-length sequences of values that all have the same type – e.g.: <code>Array&lt;string&gt;</code></li><li>Tuple types for fixed-length sequences of values where each one may have a different type – e.g.: <code>[number, string, boolean]</code></li></ul><p>In this blog post, we look at the latter – especially how to compute with tuples at the type level.</p>

<p>In this blog post, we take a closer look at template literal types in TypeScript: While their syntax is similar to JavaScript’s template literals, they operate at the type level. Their use cases include:</p><ul><li>Static syntax checking for string literals</li><li>Transforming the casing of property names (e.g. from hyphen case to camel case)</li><li>Concisely specifying large string literal union types</li></ul>

<p>The ECMAScript proposal <a href="https://github.com/tc39/proposal-regex-escaping">“RegExp escaping”</a> (by Jordan Harband and Kevin Gibbons) specifies a function <code>RegExp.escape()</code> that, given a string <code>text</code>, creates an escaped version that matches <code>text</code> – if interpreted as a regular expression.</p><p>This proposal is currently at stage 3.</p>

<p>In this blog post, we take a closer look at TypeScript enums:</p><ul><li>How do they work?</li><li>What are their use cases?</li><li>What are the alternatives if we don’t want to use them?</li></ul><p>The blog post concludes with recommendations for what to use when.</p>

<p>In order to feel more confident about my <code>tsconfig.json</code>, I decided to go through the <a href="https://www.typescriptlang.org/tsconfig/"><code>tsconfig.json</code> documentation</a>, collect all commonly used options and describe them below:</p><ul><li>You can come along for the whole ride and go through the options with me. Afterward, you should be able to understand all of your tsconfig.</li><li>Or you can skip ahead to <a href="#summary">the summary</a> at the end.</li><li>I also list <a href="#tsconfig-recommendations">recommendations for <code>tsconfig.json</code></a> by several other people.</li></ul><p>I’m curious what your experiences with <code>tsconfig.json</code> are: Do you agree with my recommendations? Did I miss anything?</p>

<p>Traditionally, we could only apply regular expression flags such as <code>i</code> (for ignoring case) to all of a regular expression. The ECMAScript feature <a href="https://github.com/tc39/proposal-regexp-modifiers">“Regular Expression Pattern Modifiers”</a> (by Ron Buckton) enables us to apply them to only part of a regular expression. In this blog post we examine how they work and what their use cases are.</p><p>Regular expression pattern modifiers attributes reached stage 4 in October 2024 and will probably be part of ECMAScript 2025.</p>

<p>The ECMAScript feature <a href="https://github.com/tc39/proposal-import-attributes">“Import Attributes”</a> (by Sven Sauleau, Daniel Ehrenberg, Myles Borins, Dan Clark and Nicolò Ribaudo) helps with importing artifacts other than JavaScript modules. In this blog post, we examine what that looks like and why it’s useful.</p><p>Import attributes reached stage 4 in October 2024 and will probably be part of ECMAScript 2025.</p>

<p>Starting with <a href="https://nodejs.org/en/blog/release/v23.6.0">v23.6.0</a>, Node.js supports TypeScript without any flags. This blog post explains how it works and what to look out for.</p>

<p>In this blog post, we look at how WebAssembly has become an ecosystem for many programming languages and what technologies enable that.</p>