consultant. Press question mark to learn the rest of the keyboard shortcuts. For further actions, you may consider blocking this person and/or reporting abuse. Well occasionally send you account related emails. This is unlikely to happen because it would require transformations that break 1-1 alignment with JavaScript. This would run counter to stated TypeScript goals of keeping parity with JavaScript. privacy statement. javascript. Is that wise? Granted, the re-ordering named parameters to sequence to expected parameters is a bit of a fickle thing, but that re-ordering does actually break 1-1 alignment. css. Already on GitHub? You signed in with another tab or window. This is problematic for .d.ts generation when the type annotation isn't an anonymous object type. Because: React function components are a very common use case for "named parameters" and destructuring with defaults. The text was updated successfully, but these errors were encountered: I have some hangups about this. I must chime-in with a report from experience.

Example: "foo.showReport(true);" versus "foo.showReport(printAlso: true);" One can't tell what "true" means in the first without digging up the parameter signature. Not sure I follow your thought. Example: You might ask "why not just manually mark the parameter as optional?" Good question! guitarero. It may be possible for TS to always translate the "regular" parameter list to an object or object literal under the hood. retrogamer. DEV Community A constructive and inclusive social network for software developers. It creates the choice of more odd syntax in common code, or not "change friendly". when it comes from a third party (example below). With you every step of your journey.

What if you didn't want the property to be optional, i.e. // We can't easily modify `SomeThirdPartyObject` here to mark `bar` as optional. Sometimes the parameter types are not easily modifyable, e.g. That's why I'm hoping either Babel or TypeScript will tackle it in the future to essentially be compiled away into positional arguments. I can't think of a reason, why JavaScript doesn't already provide "real" named arguments already optional chaining is actually available in ESNext now. developer. As I wrote in the article, I know about using object destructuring for named arguments, but I don't like this approach very much here - just doesn't feels like clean coding style to use an object inside the functions parameter definition.

You have to modify all callers with the new syntax if you change from simple parameters to ONP's. What if it makes object literals behind the scene, a kind of translator. The way you'd used named parameters in JavaScript OR TypeScript is through the use of an object: The way you'd use optional chaining is actually available in ESNext now: Thank you for giving these examples! How are you defining 1-to-1 alignment? One just normally doesn't have to know or care except for deeper debugging. Sign in I personally love the idea of forcing required parameters and providing defaults (along with some more logic) to protect on the JS consumer side. There's an argument that destructuring default is just sugar for an additional conditional assignment at the top of the function body, which would imply the parameter type shouldn't change, though again this isn't preserved by the bare parameter default behavior. climber. Typescript performs type checks on compilation only and strips all the types away, so there's never a runtime check. Some years ago I worked on a fairly large (~700k lines) JavaScript codebase that implemented a 200-line helper that permitted the following: It was used extensively, including in time-critical places such as during render operations. Update: Oh you mean for chaining arguments? Using object literals is the way we do the same thing in JS / TS. Have a question about this project? I agree 100%, however, it would drastically hinder performance as it would almost guaranteed be a runtime check in the engine. // No error since `bar` is marked as automatically optional. While there was a performance hit that could be measured with dev-tools, it was nothing compared to the usual day-to-day bottlenecks that were encountered. You could post a TS issue about it and see what feedback you get, but I think your probably going to have better luck convincing TC39 of the feature (so basically no luck at all). u/tskj already proposed that. Once you use optional named parameters, going back creates withdraw syndrome. Say we have the interface Message: And you have a factory constructor, that just provides some defaults: We use this OptionalKeys type utility, to make sure the default values are marked as optional: Suggestion: automatically mark named parameters with defaults as optional. php. Also, you are talking about overriding the intended behaviour of a third-party design object. I routinely check my required parameters. Worth a try tho. I'd like to see direct first-class support. Are you sure you want to hide this comment? As already pointed out, you can have optional named parameters via object properties. This isn't exactly what you're looking for, but what you are suggesting isn't going to happen unless it is added to the core JavaScript language. Built on Forem the open source software that powers DEV and other inclusive communities. I think making people explicitly state what they want serves the two thoughts fine as is. While TypeScript does support an indirect way to have such, it's verbose, and requires reworking calling points to add. python. The point is to say that sure, worry about performance, but perhaps rest/spread/destructuring isn't the first place you need to look these days. We're discussing named parameters and the performance hit they would be on JavaScript's runtime. And TypeScript does a whole lot more than type checking nowadays. I appreciate the symmetry with parameter defaults this would create, but I have probably a dozen objections to this. you want an explicit undefined from the consumer? Sign up for a free GitHub account to open an issue and contact its maintainers and the community. freelancer. We came with this workaround. By clicking Sign up for GitHub, you agree to our terms of service and When using "named parameters", if a parameter has a default (provided when destructuring), TypeScript should automatically mark that named parameter as optional. As a first principle, if the user writes a type annotation, we shouldn't defy that annotation without some extremely good motivation. We have the same problem, especially for factory constructors. Can you give examples for #1 and #3 in TypeScript? One could always use such object syntax "{}" to avoid the caller reformat tango, but that's cluttery in my opinion. Press J to jump to the feed. It's just not the same. Their goal is JS + types, not a divergent language. Why not just pass an optional object so you can use named parameters? If it replaced function parameters with a parameter object "under the hood" to emulate ONP's, it's still 1-to-1 translation between parameter objects and function variables. I really like C#'s optional named parameters. Just because TypeScript says it is required doesn't mean that constraint is respected on the JavaScrpt side. Other things are translated in TS, so having this be translated is not out of the norm. // (Currently this errors because `bar` is still marked as required.). TypeScript is a superset of JS, and the TS team is reluctant to add non-type oriented features to that superset unless they're going to be included in JS itself at some point. DEV Community 2016 - 2022. creator. Re-inventor extraordinaire, optimisation addict and open web advocate, PHP 8 features I wish also existed in JavaScript. It will become hidden in your post, but will still be visible via the comment's permalink. TypeScript is a typed superset of JavaScript that compiles to plain JavaScript. It's pretty much a code standard, Also, one of TS's main rules is that it is JS and JS first. TypeScript is a superset of JS, and the TS team is reluctant to add non-type oriented features to that superset unless they're going to be included in JS itself at some point. We're a place where coders share, stay up-to-date and grow their careers. Thank you for these additions! That means they can't add features on top of javascript; just type information. husband. Made with love and Ruby on Rails. Thank You! to your account, default destructuring named parameters object optional automatically. (defaultProps is supposed to solve this exact problem, but it doesn't currently work for function components: DefinitelyTyped/DefinitelyTyped#30695).

There'd be no way to opt out. When modifying defaults, we must remember to manually modify the parameter types to match any defaults we have added/removed. dad. There's zero to none performance loss. Object literals are just not the same. It makes it easy to extend the interface without re-coding the calling points, and often makes the code more legible. You're welcome to submit a proposal to the TypeScript or ECMAScript committees for consideration. TypeScript is a language for application-scale JavaScript development.