TIL

We can save all evaluated commands from our TSX REPL session to a file: $ npx tsx > const name: number = "Jake" undefined > .save output.ts Session saved to: output.ts ...

Want to get better at technical writing? I’ve been writing prose (READMEs, wikis, and this blog) with Vale for months. It’s helps me write better, faster. Here’s what I’ve learned. ...

Today I discovered tsx, a REPL that evaluates TypeScript. You can run it with npx: npx tsx And it evaluates TypeScript. > const onClick = (input: number):void => input + 1 undefined > onClick(1) 2 ...

For the golfers out there, we can combine these two lines into one: const items = await getCollection(); return items.sort(); This doesn’t work because sort() is being called on the promise returned by getCollection(): return await getCollection().sort(); // `sort()` runs on the Promise Instead, wrap the await expression in parentheses so sort() is called on the resolved value: return (await getCollection()).sort(); // `sort()` runs on the resolved array Promise documentation - MDN

Astro’s default port is 4321. Like Vite, this project is trying to convey its (rocket-launch) branding, even in this small detail. ...

Node Timeout timers have a private boolean attribute called _destroyed. It tells you if the function has been cleared: timer._destroyed; ...

Today I used JavaScript to mass-unsubscribe from a website’s email notifications. Here’s the code, followed by what I did and why. document .querySelectorAll('[role="switch"]') .forEach((element) => element.click()); ...

Reflection is an important tool in programming; it lets us examine a language’s structure. Can we reflect in JavaScript? Sort of. Some functions can be reflected with toString(): > const one = () => 1 undefined > one.toString() '() => 1' Very cool! But native functions only return this: > Math.max.toString() 'function max() { [native code] }' You must read the ECMA Script specification to know what the function is required to do. The actual implementation is written in the JavaScript engine, likely in another language like C++, which is why Node can’t show it via toString().

A vital testing skill is focusing a test. When iterating on a failing test, we want that test under microscope. The way I do this in JavaScript is .only: import {describe, expect, test} from 'vitest'; import {sum} from './sum.js'; test('adds 1 + 2 to equal 3', () => { expect(sum(1, 2)).toBe(3); }); describe.only('adding fours', () => { test('adds 4 + 4 to equal 8', () => { expect(sum(4, 4)).toBe(8); }); }); ...

JSDoc has a @deprecated tag that you can use in TypeScript, too. Here’s an example. ...