# Type system
The table below is a mapping between [scale-codec](https://docs.substrate.io/reference/scale-codec/) types (Rust) and TypeScript types that we're using for Dedot:
| Scale Codec (Rust) | TypeScript (dedot) | | |
| --------------------------------------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------- |
| u8, u16, u32,
i8, i16, i32
| `number` | | |
| u64, u128, u256,
i64, i128, i256
| `bigint` (native [BigInt](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt), not bn.js) | | |
| `bool` | `boolean` (true, false) | | |
| `Option` | `T \| undefined` | | |
| `Result` | {
isOk: true;
isErr?: false;
value: Ok
} | {
isOk?: false;
isErr: true;
err: Err
}
| |
| `Vec` | `Array` | | |
| `str` | `string` | | |
| Tuple: `(A, B)`, `()` | `[A, B]`, `[]` | | |
| Struct:
struct {
field\_1: u8,
field\_2: str
}
| {
field\_1: number,
field\_2: string
}
| | |
| Enum:
enum {
Variant1(u8),
Variant2(bool),
Variant3
}
| {
type: 'Variant1',
value: number
} | {
type: 'Variant2',
value: boolean
} | {
type: 'Variant3'
}
|
| FlatEnum:
enum {
Variant1,
Variant2
}
| `'Variant1' \| 'Variant2'` | | |