Cypress is a front-end testing utility that allows you to write UI tests using Mocha and Chai. It has auto-waits, time-travel (look back at snapshots from within test runs), and automatic discovery of tests. This blog provides a quick start for getting started with Cypress and TypeScript. Cypress NPM Packages Your package.json file will need […]
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This is just a short note on how to use an ECMAScript Proxy to intercept methods. There are plenty of examples that intercept properties, but examples with methods seem absent currently. For demonstration purposes, we’re going to intercept a very famous method. The console log method takes any number of arguments of any type. This […]
ECMAScript has an optional chaining proposal on the way (see TC39 on GitHub). It uses ?. to chain together an expression in a way that forgives a breaking chain. For example, myObj.items[0].data can fail if myObj is null, or undefined, or doesn’t have an items member, or there are no entries in the items collection, […]
Catching Null and Undefined Without Side Effects
This article simply promotes the use of the statement if (x == null) when you want to check if a value is either null or undefined. I keep on having to explain this point, because catching null or undefined without side effects is important. If we break the statement down, there is a very important […]
Exclude Files from the Visual Studio Code File Explorer
This is a quick note with an updated version on how to exclude files from the Visual Studio Code file explorer. I originally wrote about this in 2015 before the UI was as polished as it is now. I have also found I get asked about this a great deal due to conflicting information I […]
Apply TypeScript Types Honestly
TypeScript is optionally statically typed, which means you can still write dynamically typed expressions within your TypeScript programs. If you drop into a block of dynamic code, and then want to come back out into statically typed code – you’ll need to introduce the types, and are responsible for the correctness of the type you […]
Embracing the TypeScript Strict Mode
TypeScript has had the strict compiler option for a while now. It enables several more stringent checks, including two of my favourites: noImplicitAny and strictNullChecks. My summary of strict mode would be this… “If using TypeScript is better than using plain JavaScript because of the compiler warnings, why wouldn’t you want to turn the compiler […]
Deep TypeScript Destructuring
When you first encounter TypeScript (or JavaScript) destructuring it looks a little bit magic, especially in object destructuring where it looks like you are doing everything in a mirror (the names go on the right!). If you find destructuring a little confusing – strap yourselves in and we’ll rush our way to an example of […]
TypeScript Pixel Counter
In the process of writing an article on Pie Charts, I was faced with a situation where I needed to programmatically count the pixels on the pie chart in order to reverse-engineer the original values. To do this, I wrote a quick utility in TypeScript to do the following: Load an image Read each pixel […]
TypeScript Definite Assignment Assertions
TypeScript never stops improving, although most changes over the past year have been “non syntactical” – i.e. there have been a huge swathe of improvements to how types are handled, and a large slice of improvements to make the tooling even better. It has a been a while, though, since we got a new character […]
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