Structs

Decode ordered fields into typed objects.

struct(shape) decodes object entries in declaration order. Keys are appended to the active error path; values form the inferred result.

const User = struct({
    version: u8().is(1),
    id: u16(),
    name: bytes(u8()).utf8(),
});

Structs are schemas and compose recursively:

const QuestId = struct({
    group: u16(),
    number: u16(),
});

const QuestList = struct({
    id: u16(),
    quests: array(u32(), QuestId),
});

Field projection

Structs can be projected to retain or omit a subset of fields.

This is useful when you want to preserve the declarative nature of the schema, for readability purposes, but do not need certain fields to be present in the decoded value. In the example below, the last 12 bytes are reserved for the footer.

Keeping the footer field in the struct ensures the schema is as close as possible to the actual data layout.

const Table = struct({
    magic: bytes(4).ascii().is("PABR"),
    rows: array(u32(), u16()),
    footer: bytes(12).reserved(),
}).omit({ magic: true, footer: true });
// { rows: number[] }

Structs support all schema modifiers. Low-level decoders belong in custom().