Schema.org DataType in TypeScript: Structural Typing Doesn’t Cut It

Schema.org has a concept of a DataType, things like Text, Number, Date, etc. In JSON-LD, we represent these as strings or numbers, rather than array or object literals. This data could describe the name of a Person, a check-in date and time for a LodgingReservation, a URL of a Corporation, publication date of an Article, […]

Schema.org Enumerations in TypeScript

Last time, we talked about modeling the Schema.org class hierarchy in TypeScript. We ended up with an elegant, recursive solution that treats any type Thing as a “@type”-discriminated union of ThingLeaf and all the direct sub-classes of the type. The next challenge in the journey of building TypeScript typings for the Schema.org vocabulary is modeling […]

Modeling Schema.org Schema with TypeScript: The Power and Limitations of the TypeScript Type System

Recently, I published schema-dts (npm, GitHub), an open source library that models JSON-LD Schema.org in TypeScript. A big reason I wanted to do this project is because I knew some TypeScript type system features, such as discriminated type unions, powerful type inference, nullability checking, and type intersections, present an opportunity to both model what Schema.org-conformant […]

About those Side-effects in Observables, an Angular Use Case

When testing a codebase in Angular Ivy, I ran into a bunch of test failures I wasn’t seeing before. ExpressionChangedAfterItHasBeenCheckedErrors were being thrown around. In debugging these failures, I found that many of them are the results of side-effects in Observables and Observable pipe operations. I happened to describe these earlier in my piece on […]

Observables, Side-effects, and Subscriptions

My previous articles on using AsyncPipe and data refresh patterns in Angular hint at some common anti-patterns dealing with Observables. If there‚Äôs any common thread in my advice, it is: delay unpacking an Observable into its scalar types when performing logic you can rewrite as side-effect-free, leaving code with side-effects for subscription callbacks and other downstream logic. […]

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