James Sinclair

I'm so excited. ‘A Skeptic's Guide to Functional Programming with JavaScript’ is now available. To celebrate launch, it's on sale until 9 December 2022. jrsinclair.com/skeptics-guide

The Algebraic Structure of Functions, illustrated using React components ✍ @jrsinclair bit.ly/2xU9iIV

A maze that exists only as a data structure in memory is a bit useless. We need some way to make it legible to human beings. So I’ve written an article that addresses how we do that. ​jrsinclair.com/articles/2025/…

Dear JavaScript pipeline spec authors, Point-free isn't optional sugar, it's the whole point. % is an ugly hack. In fact, hack is literally in the name! 🤣 Thanks, Every functional programmer

What’s the Difference Between Ordinary Functions and Arrow Functions? — This sounds like basic stuff, but James always does a good job of digging in and explaining things... || #JavaScript #WebDev #Coding bit.ly/4lvWf1W

I felt like writing about something fun. So I wrote an article about creating mazes with JavaScript. Things got out of hand and it grew to two articles. Second one will be published real soon. jrsinclair.com/articles/2025/…

Just read up on named vs arrow functions: named ones hoist, help recursion and stack traces, and even act as constructors; arrows lexically bind this, skip prototypes and shine in callbacks. Time to stop defaulting to arrows for everything jrsinclair.com/articles/2025/…

I can't believe I haven't come across this talk by @KentBeck before. It has so much explanatory power. youtube.com/watch?v=Wazqgf…

Charity Majors talks a lot of sense, as usual: [10x Engineers exist] So what? It doesn’t matter. … What matters is how fast the team can collectively write, test, review, ship, maintain, refactor, extend, architect, and revise the software that they own charity.wtf/2025/06/19/in-…

CycleJS was the most amazing innovation in frontend since React, but sadly, it never took off… - rxjs-based: app (DOM, HTTP, state) is a stream, with no explicit state management - a single main function maps input streams (e.g. user events) to output streams (e.g. UI, effects) - side effects are declarative, managed via "drivers" that integrate with the reactive loop

I wrote a thing about all the ways you can summon a function in Javascript. It even includes a flow-chart to help check if you're picking a suitable incantation. jrsinclair.com/articles/2025/…

One of the nerdier things I've seen lately. @jrsinclair's blog generates a unique maze in the source code based on page content. A little jealous I didn't think of the idea.

What do you think? Does this theory make sense, or am I simply defending my biases?

As a side effect of this structured thinking process, you also generate automated tests that provide immediate feedback on your progress. And if you're following _all_ the steps (red, green, refactor), the code improves with every iteration.

I have a theory. People struggle with TDD because it feels like hard work. This is because many of us code to think. We're assigned a task, and we start hacking away in the IDE. The solution languidly emerges as we learn more by writing code. But TDD won't let you do that.

What would you use these for? Well, if you have large arrays, they can (sometimes) be a more efficient alternative than `.filter()` if you know where the data you want is at the start (or the end) of the array. They also come in handy when writing parsers.

The second, dropWhile(), does the opposite. It traverses your array and ignores items until a predicate returns false. Then it will give you the rest of the array.

A couple of array utilities you won't find in Array.prototype 🧵