Unpack array argument directly to parameters?

Question

I know I can do this:

function (value: [boolean, string]) {
   const [boolValue, stringValue] = value;

   // make use of boolValue and stringValue
}

But am I able to do something like this?

// doesn't work
function ([boolValue: boolean, stringValue: string]) {
   // make use of boolValue and stringValue
}

What error do you get? It's fine in ES6 (without the types), so this appears to be a TS issue. — Bergi, Oct 13 '16 at 19:16
@Bergi it gives a lot of errors doing it that way; seems like invalid syntax. First error is `] expected` (instead of `:`) — Dave Cousineau, Oct 13 '16 at 19:18
Possible duplicate of [Types in object destructuring](http://stackoverflow.com/questions/39672807/types-in-object-destructuring) — , Oct 13 '16 at 19:27
@Bergi Just so you know, I don't think I agree about removing the ES6 tag. This isn't pure ES6, but I'm compiling to ES6. That makes a difference. Maybe it doesn't matter too much in this one case, but just because something is in TypeScript doesn't mean it doesn't have anything to do with ECMAScript. — Dave Cousineau, Oct 17 '16 at 15:50
@Sahuagin I'd argue that the question is only about the type error, which is a typescript-only topic. The compilation target hardly makes a difference for that. — Bergi, Oct 17 '16 at 16:02

score 21 · Accepted Answer · answered Oct 13 '16 at 19:16

21

Ok I figured it out, might as well post as an answer. This works:

function ([boolValue, stringValue]: [boolean, string]) {
   // make use of boolValue and stringValue
}

answered Oct 13 '16 at 19:16

Dave Cousineau

3

Covered quite well at https://blog.mariusschulz.com/2015/11/13/typing-destructured-object-parameters-in-typescript. – Oct 13 '16 at 19:28
I had to wrestle with the compiler to get this to work, it was convinced that the argument [true, 'foo'] was (boolean|string)[]. I had to explicitly cast it to [boolean, string]. – Floegipoky Mar 26 '20 at 15:34

1 Answers1