JavaScript Switch Expressions???

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[EpKjelltzer]

As much as I wish this was the answer to JS's missing pattern matching, I think this is too clever. The syntax is difficult to understand, especially for beginners, and it still has all the fragility of a traditional switch statement, including fall through if you forget a return and no exhaustiveness guarantee.

[tomshieff]

I really love IIFE's, but imagine a new intern joins your team and the code is full of these. Pretty sure they would die 😆

[thomasogara]

I wish javascript had everything-expressions (switch, if, just everything)

[gerardmarquinarubio]

Me: Can we have pattern matching?
Mom: We have pattern matching at home.
Pattern matching at home:

[swapnilbhattacharjee]

Even though I don't write vanilla JS on any projects now, I do this all the time in TS.

I find this behaviour particularly useful in cases where I have to do a conditional assignment or initialisation. The benefit here is that the LSP will infer the variable as having a union type of all the return values rather than having a very broad type like number or string and that gives you a lot more of that sweet, sweet autocomplete.

I also use IIFE initialisation for throwaway functions that I don't have any reuse scope for.

One more advantage of this pattern is the need to declare fewer scoped variables whenever you need to transform the data from an external source: api, dom, fs, db, etc. into a more palatable form that the application can consume.

[po]

Pretty cool! It makes switch a functionnal expression as a ternary operator. And the syntax is pretty crystal clear

[chookingvid]

I prefer nested ternaries. They are not hard to read if formatted properly with line breaks and indents.

[Matt]

I think it depends. Declarative code is great and JS/TS needs this as a feature, but the extra syntax required for this trick may make the code harder to read, depending on the surrounding code. I'd say use it, but sparingly.

[noriller]

for something really small, yes (i use it often). but for other stuff, better to just make a function and call it

[KadenCartwright]

I think wrapping with a function and giving a coherent name, then invoking the function separately is the way I would go instead of the IIFE. If the code is in a hot path too, not having the overhead of creating a function every time could actually be significant

[GiveMeSomeMeshuggah]

Since it’s a closure, I believe that function would be allocated on the heap every single time it runs. Gotta love javascript’s memory model.

[jon]

ts-pattern is nice too! But I used IIF's like this all the time too

[theklr]

I think there's a mix. I see why people say it's clever and don't want to use it, but I also can see how this can kill nested if else issues. If you can make a case for it on the team, everyone can understand it, and it's testable? Don't see the issue.

[RandalLSchwartz]

Dart now has a switch expression with modern pattern matching. I really like it.

[paintingtheweb]

I prefer to just use an object and return a dynamic property.

...
const priorities = {...}
const p = priorities[job.priority] ?? defaultPriority
...

[ivankurchin]

How about just making if statement an expression like some other programming languages did years ago? 😂