Trying to index an array type with .get(...path)

Josh · 2025-03-24T19:58:08.824Z

```ts const schema = type('string[]'); console.log(schema.get(0).expression); ``` The code below prints "string | undefined" which at first kind of makes sense but after thinking about it, I feel like it should just be "string". While regular array indexes can return undefined, types are never actually turned into real values so an index can never actually fail. It also doesn't match TypeScript types where indexing an array type like `string[][0]` equals `string`. My use case is that I'm building an automatic form generator where I am using .get(...path) to get a specific part of the schema in a deeply nested object schema. I want to be able to effectively get the array's type but to my knowledge it's impossible to do so because any array index always adds `| undefined` so I cannot differentiate between `string[]` and `(string | undefined)[]` for example.

const schema = type('string[]');
console.log(schema.get(0).expression);

const schema = type('string[]');
console.log(schema.get(0).expression);

The code below prints "string | undefined" which at first kind of makes sense but after thinking about it, I feel like it should just be "string". While regular array indexes can return undefined, types are never actually turned into real values so an index can never actually fail. It also doesn't match TypeScript types where indexing an array type like

string[][0]

string[][0]

equals

string

string

.

My use case is that I'm building an automatic form generator where I am using .get(...path) to get a specific part of the schema in a deeply nested object schema. I want to be able to effectively get the array's type but to my knowledge it's impossible to do so because any array index always adds

| undefined

| undefined

so I cannot differentiate between

string[]

string[]

and

(string | undefined)[]

(string | undefined)[]

for example.

arktype•12mo ago•

36 replies

Josh

Trying to index an array type with .get(...path)

const schema = type('string[]');
console.log(schema.get(0).expression);

const schema = type('string[]');
console.log(schema.get(0).expression);

string[][0]

string[][0]

equals

string

string

| undefined

| undefined

so I cannot differentiate between

string[]

string[]

and

(string | undefined)[]

(string | undefined)[]

for example.

Trying to index an array type with .get(...path)

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