Can :[Interface] be considered a correct array declaration in Typescript?

My TypeScript codebase is filled with code snippets like the one below...

export interface SomeType {
    name: string;
}

export interface SomeComposedType {
    things: [SomeType];
}

Everything was working smoothly until I started experiencing issues such as

Property '0' is missing in type

as well as

Argument of type 'SomeType[]' is not assignable to parameter of type '[SomeType]'

I'm quite perplexed by these errors. I had believed that

let x:SomeType[] = []

is the same as

let x: Array<SomeType> = []

but is

let x:[SomeType] = []

also equivalent and accurate?

Answer №1

Incorrect. In TypeScript, [SomeType] actually represents a tuple type, which is an array containing one element of type SomeType

For instance, [string, number] would correspond to an array like ["test", 0]

Answer №2

Indeed, when you see let x: [SomeType], it indicates that x is an Array with one element of type SomeType

If you wish to define an array containing elements of SomeType, you can simply use either SomeType[] or Array<SomeType>

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