Migrating a Legacy JavaScript Codebase to TypeScript - JSJ 680

Migrating a Legacy JavaScript Codebase to TypeScript - JSJ 680

In this episode, Dan and I (Steve) dove deep into what turned out to be a surprisingly complex, yet incredibly insightful topic: gradually migrating a massive legacy JavaScript project over to TypeScript. We're talking about nearly 1,000 JS files, 70,000+ lines of code, and years of developer history—all transitioning carefully to a typed, modern future.

Dan walked us through how he started by setting up the project for success before converting even one file—getting CI/CD ready, setting up tsconfig.json, sorting out test dependencies, dealing with mock leaks, and even grappling with quirks between VS Code and WebStorm debugging.

We talked tools (like TS-ESLint, concurrently, and ts-node), why strict typing actually uncovered real bugs (and made the code better!), and why it’s crucial not to touch any .js files until your TypeScript setup is rock solid.

Key Takeaways:
  • Gradual migration is 100% possible—and often better—than ripping the bandaid off.
  • TypeScript can and will catch bugs hiding in your JavaScript. Be prepared!
  • Use VS Code extensions or TS-Node to support your devs’ tooling preferences.
  • Don't underestimate the setup phase—it’s the foundation of long-term success.
  • Start small: Dan's team converted just one file at first to test the whole pipeline.
If you’re sitting on a legacy JS project and dreaming of TypeScript, this episode is your blueprint—and your warning sign.

Become a supporter of this podcast: https://www.spreaker.com/podcast/javascript-jabber--6102064/support.

Episoder(737)

113 JSJ Community Dynamics with Reginald Braithwaite

113 JSJ Community Dynamics with Reginald Braithwaite

The panelists talk to Reginald Braithwaite about the dynamics of the JavaScript community.Special Guest: Reginald Braithwaite. Support this podcast at — https://redcircle.com/javascript-jabber/donat...

18 Jun 201449min

112 JSJ Refactoring JavaScript Apps Into a Framework with Brandon Hays

112 JSJ Refactoring JavaScript Apps Into a Framework with Brandon Hays

The panelists talk about refactoring JavaScript Apps Into a Framework with Brandon Hays.Special Guest: Brandon Hays. Support this podcast at — https://redcircle.com/javascript-jabber/donationsPrivac...

11 Jun 201459min

111 JSJ The Ember.js Project with Erik Bryn

111 JSJ The Ember.js Project with Erik Bryn

The panelists talk to Erik Bryn about the Ember.js project.Special Guest: Erik Bryn. Support this podcast at — https://redcircle.com/javascript-jabber/donationsPrivacy & Opt-Out: https://redcircle.c...

4 Jun 20141h 8min

110 JSJ Zones with Brian Ford

110 JSJ Zones with Brian Ford

The panelists discuss zone.js with Brian Ford.Special Guest: Brian Ford. Support this podcast at — https://redcircle.com/javascript-jabber/donationsPrivacy & Opt-Out: https://redcircle.com/privacyBe...

28 Mai 201438min

109 JSJ Dependency Injection in JavaScript with Vojta Jína & Misko Hevery

109 JSJ Dependency Injection in JavaScript with Vojta Jína & Misko Hevery

The panelists discuss dependency injection with Vojta Jína & Misko Hevery.Special Guests: Miško Hevery and Vojta Jína. Support this podcast at — https://redcircle.com/javascript-jabber/donationsPriv...

21 Mai 201446min

108 JSJ AngularJS with Igor Minar

108 JSJ AngularJS with Igor Minar

The panelists have Igor Minar back on the show to discuss AngularJS in detail.Special Guest: Igor Minar. Support this podcast at — https://redcircle.com/javascript-jabber/donationsPrivacy & Opt-Out:...

14 Mai 201446min

107 JSJ ClojureScript & Om with David Nolen

107 JSJ ClojureScript & Om with David Nolen

The panelists talk to David Nolen about ClojureScript and Om.Special Guest: David Nolen. Support this podcast at — https://redcircle.com/javascript-jabber/donationsPrivacy & Opt-Out: https://redcirc...

7 Mai 201452min

106 JSJ Protractor with Julie Ralph

106 JSJ Protractor with Julie Ralph

The panelists talk to Julie Ralph about AngularJS's protractor.Special Guest: Julie Ralph. Support this podcast at — https://redcircle.com/javascript-jabber/donationsPrivacy & Opt-Out: https://redci...

30 Apr 201448min

Populært innen Business og økonomi

stopp-verden
lydartikler-fra-aftenposten
dine-penger-pengeradet
e24-podden
rss-penger-polser-og-politikk
rss-borsmorgen-okonominyhetene
finansredaksjonen
pengepodden-2
pengesnakk
utbytte
tid-er-penger-en-podcast-med-peter-warren
rss-sunn-okonomi
stormkast-med-valebrokk-stordalen
morgenkaffen-med-finansavisen
livet-pa-veien-med-jan-erik-larssen
lederpodden
okonomiamatorene
rss-markedspuls-2
flypodden
rss-fa-makro