极客Alex
3/14/2025
Hey devs! 👋
So, I've been pulling my hair out over this little JavaScript/TypeScript quirk. I’m dealing with some async operations and property ordering in objects, and it's been a bit of a mess. 😅 Here’s the deal: I want to declare object properties without giving them a value right away to maintain the property order. You know, just like how we used to do with variables in old-school JS, like var value1, value2; and deal with them later.
I’ve got a setup like this:
const props = {}; const propsSet = getters.map(async ([key, getValue]) => { props[key] = await getValue(); // 🙃 trying to keep the order }); await Promise.all(propsSet);
Now, the async nature of it means sometimes I get { foo: …, bar: … } and other times { bar: …, foo: … }. Super annoying when order matters. I tried initializing the properties as soon as I could:
const propsSet = getters.map(async ([key, getValue]) => { props[key] = null; // initial token to keep things in order props[key] = await getValue(); });
This works fine in plain JS, but TypeScript isn't happy with it. I get yelled at by the compiler because my "initial token" (like null) doesn't match the expected type. 😤
I've tried using // @ts-expect-error to hush the compiler:
// @ts-expect-error: shush, compiler! props[key] = null;
But all this shushing doesn't feel right... 😩
So, I'm wondering, is there any way (or upcoming proposal, maybe?) to declare object properties without initializing them right off the bat? I'm not looking for ways to reorder properties after the fact—just a clean, efficient way to set things up properly from the start.
Any magic tricks or best practices out there? Would love any advice you can throw my way! 😄🙏
P.S. If there’s a secret TypeScript spell book I’m missing, do let me know! 📚✨
Thanks! 🚀
程序员小李
3/14/2025
Hey there! 👋 I totally feel your frustration with handling async operations and property ordering in TypeScript. Been there myself, and it's definitely one of those head-scratchers. 😅
I remember wrangling with a similar issue where I needed to maintain the order of properties but found TypeScript to be a bit too strict for my liking. The quirks can be a bit annoying, but there's a way around this!
So, let's dive into it. You're on the right track with initializing your properties early, but the TypeScript type system can be quite the stickler. Here's a friendly approach to keep both your code and the TypeScript compiler happy:
interface Props { foo?: string; bar?: string; }
undefined or null as placeholders that TypeScript will accept if your interface indicates they're optional.const props: Props = { foo: undefined, // or null bar: undefined, // or null }; const getters = [ ['foo', async () => 'value for foo'], ['bar', async () => 'value for bar'], ]; const propsSet = getters.map(async ([key, getValue]) => { // This step ensures TypeScript knows these keys will be defined props[key as keyof Props] = await getValue(); }); await Promise.all(propsSet);
props[key as keyof Props] = await getValue();
Interfaces are Your Friends: They help guide TypeScript in knowing what to expect, which can reduce errors and makes your code more self-documenting.
Type Guard Functions: If you find yourself dealing with dynamic keys often, consider writing small type guard functions to assert types safely.
Common Mistake: Avoid using any just to bypass errors. It might be tempting, but it defeats the purpose of TypeScript's type safety.
Review Type Definitions: Sometimes, revisiting type definitions helps catch any misunderstandings with optional properties.
I hope this helps you maintain that property order without getting on TypeScript's bad side. Trust me, once everything clicks, it feels like magic! ✨
If you run into more issues or have any questions, feel free to ask. We're all in this coding journey together, and I'm here to help you out! 🚀
Happy coding and best of luck! 😊