How JavaScript source maps actually work

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Plus htmx 4 alpha, embedding JS/TS anywhere with Hako, Vue 3 data components, and using the URL to store state. |

#​760 — November 7, 2025

Read on the Web
Together with  WorkOS

JavaScript Weekly

The Inner Workings of JavaScript Source Maps — Ever wondered how devtools can magically turn mangled, minified JavaScript back into readable source while debugging? Zero magic; that's a source map doing its job. But how do source maps actually work under the hood?

Manoj Vivek

Ship Secure MCP Auth Without Relying on API Keys — API keys are hard to scope and break user flows. WorkOS Connect delivers a fully compliant OAuth 2.1 flow. It handles PKCE, scopes, user consent, and secure token issuance out of the box.

WorkOS sponsor

Anders Hejlsberg's Take on the Rise of TypeScript — The co-creator of TypeScript says he's 'floored' by the language's success (now the number one language on GitHub in 2025), shares a little info on the on-going compiler rewrite in Go, and the increasing role of AI.

The GitHub Blog

Embedding TypeScript with Hako — A technical look at the Hako JavaScript engine. It runs in WebAssembly so can be more easily embedded in more environments, including mobile apps.

Andrew Sampson

IN BRIEF:

RELEASES:

📖  Articles and Videos

▶  The Talk Videos from CascadiaJS 2025 — CascadiaJS took place a month ago and the talk videos have been gradually rolling out onto YouTube. You can learn more about TanStack with Jack Herrington, the origin story of JavaScript with Annie Sexton, the Web Monetization API with Ioana Chiorean, and more.

CascadiaJS

High-Performance Syntax Highlighting with the CSS Custom Highlight API — Now supported in all major browsers, the CSS Custom Highlight API provides a mechanism for styling arbitrary text ranges in a document by using JavaScript to create the ranges, and CSS to style them.

Pavitra Golchha

How to Create a Virtual Green Screen Using the Vonage Video API — Transform video calls with virtual green screens using the Vonage Video API and HTML5 canvas.

Vonage sponsor

How to Throttle Specific Requests in Chrome DevTools — Chrome DevTools has supported network throttling for a long time but you can now throttle requests to specific URLs or domains too, which could be ideal if you want to see how your site handles the failure of third party scripts.

Matt Zeunert

?! Importing Node Modules from BitTorrent — A fascinating demo of the power of Node.js's customization hooks for overriding import behavior.

Evan Hahn

Advanced Beginner's Guide to ClojureScript — An introduction to a compiler for the functional Clojure Lisp dialect that produces JavaScript.

Roman Liutikov

📄 Handling Time and Mock Clocks in Tests Andrew Scott (Angular)

📄 Zod + TypeScript: Schema Validation Made Easy Hassan Djirdeh

📄 Next.js 16: What's New and What It Means for Frontend Devs Abiola Farounbi (LogRocket)

🛠 Code & Tools

Perspective 4.0: High Performance Analytics and Data Visualization Component — Originally built by JP Morgan, this data visualization component, built in C++ and compiled to WebAssembly, is well-suited for large and real-time streaming datasets. The demo on the homepage lets you try visualization types at up to 1000 changes per second. v4.0 sees the project move to the OpenJS Foundation.

OpenJS Foundation

💡 Perspective comes with a rich set of examples with full code demonstrating how to use it, like this streaming example.

Agentic Postgres: Let Your Agents Cook — Build AI apps faster: Postgres with built-in memory, search, and free forkable DBs. Try it free on Tiger.

Tiger Data sponsor

Vue Data UI 3.6: Vue Components Library for Data Storytelling — There's a lot packed into this suite of components, including basic chart types through to donuts, sparklines, world views, stacks, heatmaps, word clouds, and more. Definitely worth a look if you're using Vue. Live examples.

Alec Lloyd Probert

🖼️ image-dimensions: Get the Dimensions of Images — A zero-dependency way to get the pixel width and height of JPEG, PNG/APNG, GIF, WebP, AVIF and HEIF images in any modern JavaScript environment.

Sindre Sorhus

React Syntax Highlighter: A Code Syntax Highlighting Component — If you need to show off source code in your React app somewhere, this is a component that does the job. GitHub repo.

Conor Hastings

CSSOM: A CSS Parser Written in Pure JavaScript — Also a partial implementation of CSS Object Model.

Nikita Vasilyev

  • debounce 3.0 – Delay function calls until a set time elapses after the last invocation. Now a pure ES module.

  • bcrypt.js 3.0.3 – Optimized bcrypt in pure JavaScript, even in the browser.

  • Marked 17.0 – Markdown parser and compiler. (Docs.)

  • AlaSQL.js 4.8 – Isomorphic JavaScript SQL database.

  • fast-copy 4.0 – A fast deep object copier.

📰 Classifieds

Still writing tests manually? See why modern engineering teams like Dropbox, Notion and Wiz rely on Meticulous to run E2E UI tests.

🔎 Search your GitHub Actions logs instantly. No more endless scrolling through CI failures. Try Depot's new log search and find errors in seconds.

📢  Elsewhere in the ecosystem

A roundup of some other interesting stories in the broader landscape:

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