# Writing Advanced CWL JS Expressions in TypeScript **URL:** \ **Category:** CWLCon 2023\ **Created:** [February 24, 2023, 1:44pm UTC](https://cwl.discourse.group/t/writing-advanced-cwl-js-expressions-in-typescript/755 "2023-02-24T13:44:56Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![alexiswl](https://yyz2.discourse-cdn.com/free1/user_avatar/cwl.discourse.group/alexiswl/32/93_2.png) [@alexiswl](https://cwl.discourse.group/u/alexiswl)\ **Post date:** [February 24, 2023, 1:44pm UTC](https://cwl.discourse.group/t/writing-advanced-cwl-js-expressions-in-typescript/755/1 "2023-02-24T13:44:56Z")
Presenter: [Alexis Lucattini](https://orcid.org/0000-0001-9754-647X), University of Melbourne Centre for Cancer Research (UMCCR) @alexiswl [Schedule](https://cwl.discourse.group/t/schedule-of-confirmed-talks/753): - Session 2: 🌍 🌏 (EMEA-APAC) Wednesday, March 1st 07:00 - 11:00 UTC / 16:00 - 20:00 Japanese Standard Time - Session 3: 🌏 🌎 (APAC-Americas) Thursday, March 2nd 19:00 - 23:00 US EST Friday, March 3rd 00:00 - 04:00 UTC / 09:00 - 13:00 Japanese Standard Time > Widespread use of CWL JavaScript Expressions is often restricted to simple one-line code fragments. > > It is without dispute that writing complex, yet easily readable, ES5.1 conformant, JS code for CWL is inherently very difficult. > > For many developers, interaction with CWL objects such as File, Dirent, Directory or custom-made schemas can prove to be a steep-learning curve. > It is therefore no surprise that writing complex CWL JS expressions is generally discouraged. > It is, however, sometimes necessary. > > In this presentation we introduce the concept of writing our CWL JS expressions in TypeScript. > > We will discuss the benefits of this approach, such as: > > - type-hinting for CWL Objects, > - compatible ‘transpilation’, > - unit-testing with the jest framework > - auto TypeScript-Interface creation for custom CWL Schemas. > > We will view some simple and complex use-cases of CWL JS Expressions, the selection of open CWL TS packages and some caveats to consider for TypeScript in CWL. > > We will conclude by noting that writing complex CWL JS expressions is a difficult task and alternative options should be considered. Using TypeScript may alleviate some existing challenges faced by developers writing CWL JS expressions. - Slides: [https://bit.ly/typescript-in-cwl-powerpoint](https://bit.ly/typescript-in-cwl-powerpoint) - CWL-ICA GitHub Repository: [https://github.com/umccr/cwl-ica](https://github.com/umccr/cwl-ica) - Releases Page: [https://github.com/umccr/cwl-ica/releases](https://github.com/umccr/cwl-ica/releases) - TypeScript Wiki Page: [https://github.com/umccr/cwl-ica/wiki/TypeScript](https://github.com/umccr/cwl-ica/wiki/TypeScript) - cwl-ica cli code base: [https://github.com/umccr/cwl-ica-cli](https://github.com/umccr/cwl-ica-cli) - Jest Testing Framework: [https://jestjs.io/](https://jestjs.io/) - Comparison of rabix cwlts vs cwl-ts-auto TypeScript modules: [https://github.com/common-workflow-lab/cwl-ts-auto/issues/23](https://github.com/common-workflow-lab/cwl-ts-auto/issues/23) Please leave your questions for the presenter below! [![](https://global.discourse-cdn.com/free1/uploads/cwl1/original/1X/748111ef0626da7029fa7a6e97bf7ffc83896c89.jpeg "Writing Advanced CWL JS Expressions in TypeScript") ](https://www.youtube.com/watch?v=Dn-zjkHtra8) As an alternative to YouTube, this presentations is also available on ConfTube https://conf.tube/videos/embed/d92d37eb-6d20-4aba-8c10-8efd480ea651 ---
**Author:** ![brunokinoshita](https://yyz2.discourse-cdn.com/free1/user_avatar/cwl.discourse.group/brunokinoshita/32/226_2.png) [@brunokinoshita](https://cwl.discourse.group/u/brunokinoshita)\ **Post date:** [March 1, 2023, 7:45am UTC](https://cwl.discourse.group/t/writing-advanced-cwl-js-expressions-in-typescript/755/2 "2023-03-01T07:45:08Z")
Hi Alexis! Q. Just had a look at [GitHub - umccr/cwl-ica: A collection of cwl-ica workflows along with a user guide for the commands to use and contributions guide](https://github.com/umccr/cwl-ica), and I found some `package.json` files with ts, jest, etc. Is there any example that demonstrates CWL → TS with tests & coverage? Q. You mentioned the `node_modules` in Yarn, but Yarn V3 and PnP could be a possible solution. (You answered that in the meeting, but asking here too for others/posterity). Thanks! ---
**Author:** ![alexiswl](https://yyz2.discourse-cdn.com/free1/user_avatar/cwl.discourse.group/alexiswl/32/93_2.png) [@alexiswl](https://cwl.discourse.group/u/alexiswl)\ **Post date:** [March 1, 2023, 10:42pm UTC](https://cwl.discourse.group/t/writing-advanced-cwl-js-expressions-in-typescript/755/3 "2023-03-01T22:42:49Z")
Hi Bruno, > Is there any example that demonstrates CWL → TS with tests & coverage? The only CWL → TS is the conversion of CWL schemas to TypeScript interfaces. These exist inside the schemas directory. I don’t have tests for this sorry, but if you start with [cwl-ica/bclconvert-settings\_\_4.0.3.ts](https://github.com/umccr/cwl-ica/blob/339c72cf06fda872806449a89a454907793a01ad/schemas/bclconvert-run-configuration/2.0.0--4.0.3/bclconvert-run-configuration__2.0.0--4.0.3.yaml) it shows it can handle very complex schemas. For example tests showing TS to CWL expressions please checkout [the TypeScript wiki page](https://github.com/umccr/cwl-ica/wiki/TypeScript) > but Yarn V3 and PnP could be a possible solution Yes it sure could be, I’ll add something to the TypeScript wiki above, in the typescript expressions directory, yarn will create a file called .yarnrc.yml You may set this to nodeLinker: pnp and see if that works for you?