typescript 如何限制函数参数的值？

Question

// data 数据是固定的
const data = [{},{},{}]

function set(index){
 // ...
}

如何限制参数 index 只能是 0 1 2 （数组的下标）

Answer 1

这个意思？？？

type i = 0|1|2

function set(index:i){
 // ...
}

如果是这个意思哪就可以这样写

const data = [{},{},{}] as const 


type ArrIndex<T extends readonly any[]> = Exclude<Partial<T>["length"], T["length"]>
type IndexType = ArrIndex<typeof data> 
function set(index:IndexType){

}


set(2) //ok
set(3) //eror

Answer 2

function set(index: 0 | 1 | 2) {

// ...

}

Answer 3

type TupleIndices<A extends readonly any[], Acc = never>
    = A extends readonly [any, ...infer T]
    ? TupleIndices<T, Acc | T['length']>
    : Acc

const data = [{},{},{}] as const
function set(index:TupleIndices<typeof data>){
 // ...
}