The project I’m working on has a Node.js back end written in TypeScript, with a PostgreSQL database for persistence. We had a production user who encountered an error when the system tried to insert a row into a table that had an integer column in it. The value it was trying to insert was 239.99999999999997, so it made sense that PostgreSQL was complaining about it being “invalid input syntax for an integer.”
TypeScript
“Understanding TypeScript’s Structural Type System” at Strange Loop 2018
I'm super excited to be giving a talk about TypeScript at Strange Loop this year! The talk, “Understanding TypeScript's Structural Type System,” covers some of the deeper and most exciting ideas at the heart of TypeScript's namesake feature.
Read more on “Understanding TypeScript’s Structural Type System” at Strange Loop 2018…
Creating a Drag-and-Drop File Uploader with React & TypeScript
A while ago, I was working on a project based off the Atomic SPA Starter Kit, which uses TypeScript, React, and GraphQL. One of the features we needed to build was a file upload component that supported dragging and dropping a file from a separate window onto the UI. Read more on Creating a Drag-and-Drop File Uploader with React & TypeScript…
Correctly Managing Concurrency in JavaScript
More times than I can count, I’ve found myself needing better concurrency primitives in JavaScript (or TypeScript) applications. Almost anything you might need is possible using the Promise API, but promises are complex, and there are many subtleties that easily manifest bugs. Read more on Correctly Managing Concurrency in JavaScript…
Migrating an Ejected Create React App to TypeScript
I love Create React App, and I also love TypeScript. That means I really love react-scripts-ts, which is a great way to spin up a new SPA for experimental purposes.
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Mocking TypeScript Modules with Sinon
Lately, my team has been looking for better ways to create and maintain mocks in our TypeScript project. In particular, we wanted an easy way to mock out modules that we built using Sinon.JS. Read more on Mocking TypeScript Modules with Sinon…
Styling Custom Components in React Native Using TypeScript
I recently ran into an issue with providing style properties to custom React Native components written in TypeScript. When defining the type of the style property, we were using the ViewStyle and TextStyle types provided by React Native.
Read more on Styling Custom Components in React Native Using TypeScript…
Type-Safe Object Merging (TypeScript 2.8 Edition)
There are times when you want to merge two generic types in TypeScript, and type inference just isn’t doing it for you. Object.assign’s typing isn’t as precise as it could be, and spreading generics still doesn’t work. I’ve found a way to implement typing when merging objects using some of the new features in TypeScript 2.8.
Read more on Type-Safe Object Merging (TypeScript 2.8 Edition)…
Statically Typed Data Validation with JSON Schema and TypeScript
One super common problem on TypeScript projects is figuring out how to validate data from external sources and tie that validated data to TypeScript types. In these situations, you generally have a few options:
- Define types and validations separately, and type them together with Type Guards.
- Use an internal DSL such as io-ts to build both a validator and the TypeScript type at the same time.
- Use an external DSL such as JSON Schema to define the validator, and derive the TypeScript type from there.
Read more on Statically Typed Data Validation with JSON Schema and TypeScript…
Simple Error Either in TypeScript
When writing a function, I often want to return either the successful value or an error. Given that my current project is in TypeScript, we came up with a nice little Either pattern for returning successes or errors. Read more on Simple Error Either in TypeScript…