Field types

Generated field types follow the Protobuf field kind. create() supplies runtime defaults; TypeScript types describe the shape stored on the message.

Scalars

Protobuf type	ECMAScript type	Notes	Runtime default
string	string	UTF-8	""
bool	boolean		false
bytes	Uint8Array		new Uint8Array(0)
double	number	64-bit float	0
float	number	32-bit float	0
int32	number	32-bit signed varint	0
uint32	number	32-bit unsigned varint	0
int64	bigint	64-bit signed varint	0n
uint64	bigint	64-bit unsigned varint	0n
fixed32	number	32-bit unsigned fixed	0
fixed64	bigint	64-bit unsigned fixed	0n
sfixed32	number	32-bit signed fixed	0
sfixed64	bigint	64-bit signed fixed	0n
sint32	number	32-bit signed varint	0
sint64	bigint	64-bit signed varint	0n

If bigint is unavailable in your environment, 64-bit integer fields still round-trip safely, but use string values at runtime instead.

Use jstype = JS_STRING when you want string output for a 64-bit field:

int64 field = 1 [jstype = JS_STRING];

With Buf managed mode, apply that option automatically:

managed:
  enabled: true
  override:
    - field_option: jstype
      value: JS_STRING

Message fields

Message fields become optional properties. With exactOptionalPropertyTypes, the generated type includes undefined explicitly.

User manager = 4;

manager?: User | undefined;

Message fields do not have default values in Protobuf.

Enum fields

Enum fields use the generated TypeScript enum and default to the first declared value.

phoneType: PhoneType;

TypeScript enums can convert between numeric values and string names:

const val: PhoneType = PhoneType.MOBILE;
const name = PhoneType[val]; // "MOBILE"

Protobuf has open and closed enums. Open enums can contain numeric values that are not declared in the generated TypeScript enum, so code that receives data from newer schemas should handle unknown enum numbers.

Repeated fields

Repeated fields become arrays.

repeated string locations = 5;

locations: string[];

New messages created with create() initialize repeated fields to empty arrays.

Map fields

Map fields become record-like objects.

map<string, string> projects = 6;

projects: { [key: string]: string };

New messages created with create() initialize map fields to empty objects. Protobuf-ES uses objects instead of ECMAScript Map because objects fit better with current JavaScript and TypeScript tooling.

Well-known type fields

Some well-known types use JavaScript-friendly representations. google.protobuf.Struct fields become JsonObject:

struct?: JsonObject | undefined;

Wrapper messages become unboxed optional primitives:

boolValueField?: boolean | undefined;

See Well-known types for the full list of precompiled exports and helper functions.