Does TypeScript allow type aliases?
TypescriptAliasTypescript Problem Overview
So I wish I could use an alias to an ugly type that looks like this:
Maybe<Promise<Paged<Carrier>, Problem>>[]
Something like:
import Response = Maybe<Promise<Paged<Carrier>, Problem>>[];
Is there a way to do type aliases in TypeScript?
Typescript Solutions
Solution 1 - Typescript
From version 1.4 Typescript supports type aliases (source).
> Type Aliases
>
> You can now define an alias for a type using the type keyword:
>
> type PrimitiveArray = Array
And from version 1.6 Typescript supports generic type aliases (source).
>Generic type aliases
>
>Leading up to TypeScript 1.6, type aliases were restricted to being simple aliases that shortened long type names. Unfortunately, without being able to make these generic, they had limited use. We now allow type aliases to be generic, giving them full expressive capability.
>
> type switcharoo
Solution 2 - Typescript
TypeScript supports imports, e.g.:
module A {
export class c {
d: any;
}
}
module B {
import moduleA = A;
var e: moduleA.c = new moduleA.c();
}
module B2 {
import Ac = A.c;
var e: Ac = new Ac();
}
Update 1
Since TS 1.4 we can use type declarations:
type MyHandler = (myArgument: string) => void;
var handler: MyHandler;
Since TS 1.6 we can use local type declarations:
function f() {
if (true) {
interface T { x: number }
let v: T;
v.x = 5;
}
else {
interface T { x: string }
let v: T;
v.x = "hello";
}
}
Solution 3 - Typescript
A poor man's solution is to declare a dummy variable (e.g. t
) with the desired type and use typeof t
instead of the long type expression:
var t: { (x: number, f: { (foo: string, bar:boolean): void }): void };var f: typeof t; var g: typeof t;