This code snippet is not functioning as expected
type Foo = number[]
type Bar = string[]
function move(x: Foo | Bar) {
const v = x.splice(0, 1)
x.splice(1, 0, ...v)
}
The issue arises because v is inferred to be of type number[] | string[], which is not directly assignable to either number or string. Any suggestions on how to address this?
unknownWhen dealing with a generic operation on an array like moving elements, the specific type of the array is not crucial. You can simply indicate that the function will accept any array using unknown[] or `Array:
type Foo = number[]
type Bar = string[]
function move(x: unknown[]) {
const v = x.splice(0, 1)
x.splice(1, 0, ...v)
}
declare const arr: Foo | Bar;
move(arr); //OK
If specifying the type is relevant, use generics and restrict it to arrays:
type Foo = number[]
type Bar = string[]
function move<T extends Array<unknown>>(x: T) {
const v = x.splice(0, 1)
x.splice(1, 0, ...v)
}
declare const arr: Foo | Bar;
move(arr); //OK
This approach can be beneficial to specify expected types in a call, leading to a compilation error if they do not match:
move<string[] | number[]>(arr); // OK
move<string[] | number[] | boolean[]>(arr); // OK
move<string[] | boolean[]>(arr); // error
move<string[]>(arr); // error
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