Jettison is an instructions-based JSON encoder inspired by bet365/jingo, with a richer features set, aiming at 100% compatibility with the standard library.


$ go get -u

:exclamation: Requires Go1.12+, due to the usage of io.StringWriter.

Key points

  • Fast, see benchmarks
  • Zero allocations on average
  • Behavior almost identical to the standard library, by default
  • No code generation required
  • Clear and simple API
  • Options available to configure encoding
  • Native support for time.Time and time.Duration


The goal of Jettision is to take up the idea introduced by the bet365/jingo package and build a fully-featured JSON encoder around it, that comply with the behavior of the encoding/json package. Unlike the latter, Jettison does not use reflection during marshaling, but only once to create the instructions set for a given type ahead of time. The drawback to this approach requires to instantiate a separate encoder for each of the types that needs to be marshaled.

The package aims to have a behavior similar to that of the standard library for all types encoding and struct tags, meaning that the documentation of the Marshal function is applicable for Jettison, with a few exceptions described in this section. As such, most of the tests compare their output against it to guarantee that.


First, create a new encoder for the type that needs to be marshaled, and compile the instructions set.

import ""

type x struct {
    A string `json:"a,omitempty"`
    B int    `json:"b"`
enc, err := jettison.NewEncoder(x{})
if err != nil {
    // handle error
err = enc.Compile()
if err != nil {
    // handle error

Note that if you don't invoke the Compile method manually, the instructions will be generated once, on the first call to the Encode method.

xx := x{
    A: "Loreum",
    B: 42,
var buf bytes.Buffer
if err := enc.Encode(&xx, &buf); err != nil {
    // handle error
// {"a":"Loreum","b":42}

The second parameter of the Encode method is an interface that groups the io.Writer, io.StringWriter and io.ByteWriter interfaces. In the above example, we use a new bytes.Buffer instance, which implements the three interfaces mentioned.


Opt-in options are available to customize the behavior of the package. The third parameter of the Encode method is variadic and accept a list of functional options described below.

Option Description
TimeLayout Defines the layout used to encode time.Time values. time.RFC3339Nano is the default.
DurationFormat Defines the format used to encode time.Duration values. DurationString is the default. See DurationFmt for the complete list of formats available.
UnixTimestamp Encode time.Time values as JSON numbers representing Unix timestamps.
UnsortedMap Disables map keys sort.
ByteArrayAsString Encodes byte arrays as JSON strings rather than JSON arrays. The output is subject to the same escaping rules used for the string type, unless the option NoStringEscaping is also specified.
RawByteSlices Disables base64 default encoding used for byte slices.
NilMapEmpty Encodes nil maps as empty JSON objects rather than null.
NilSliceEmpty Encodes nil slices as empty JSON arrays rather than null.
NoStringEscaping Disables strings escaping.

Differences with encoding/json

  • Strings are not coerced to valid UTF-8 by replacing invalid bytes with the Unicode replacement rune, and the brackets < and > or ampersand & are not escaped. Escaping is only applied to bytes lower than 0x20 and those described in the JSON spec.

  • time.Time and Time.Duration types are handled natively by the package. For the first, the encoder doesn't invoke the MarshalJSON/MarshalText methods, but use time.AppendFormat directly. For the second, it isn't necessary to implements the json.Marshaler or encoding.TextMarshaler interfaces, the encoder uses the result of the methods Minutes, Seconds, Nanoseconds or String based on the duration format configured.

  • Nil map keys instances implementing the TextMarshaler interface are encoded as an empty string, while the encoding/package currently panic because of that. See this issue for more details.


Ubuntu 16.04.6 LTS, Intel(R) Core(TM) i5-6600 CPU @ 3.30GHz
go version go1.12.5 linux/amd64


Basic object with fields of type string, int and bool. source


name time/op
SimplePayload/standard-4 615ns ± 1%
SimplePayload/jsoniter-4 645ns ± 1%
SimplePayload/gojay-4 444ns ± 4%
SimplePayload/jettison-4 400ns ± 1%

name speed
SimplePayload/standard-4 219MB/s ± 1%
SimplePayload/jsoniter-4 209MB/s ± 1%
SimplePayload/gojay-4 304MB/s ± 4%
SimplePayload/jettison-4 337MB/s ± 1%

name alloc/op
SimplePayload/standard-4 144B ± 0%
SimplePayload/jsoniter-4 152B ± 0%
SimplePayload/gojay-4 512B ± 0%
SimplePayload/jettison-4 0.00B

name allocs/op
SimplePayload/standard-4 1.00 ± 0%
SimplePayload/jsoniter-4 2.00 ± 0%
SimplePayload/gojay-4 1.00 ± 0%
SimplePayload/jettison-4 0.00


Payload with a variety of composite Go types, such as struct, multi-dimensions array, and slice, with pointer and non-pointer value types. source



name time/op
ComplexPayload/standard-4 2.34µs ± 0%
ComplexPayload/jsoniter-4 2.18µs ± 2%
ComplexPayload/jettison-4 1.37µs ± 1%

name speed
ComplexPayload/standard-4 165MB/s ± 0%
ComplexPayload/jsoniter-4 178MB/s ± 2%
ComplexPayload/jettison-4 283MB/s ± 1%

name alloc/op
ComplexPayload/standard-4 416B ± 0%
ComplexPayload/jsoniter-4 472B ± 0%
ComplexPayload/jettison-4 0.00B

name allocs/op
ComplexPayload/standard-4 1.00 ± 0%
ComplexPayload/jsoniter-4 3.00 ± 0%
ComplexPayload/jettison-4 0.00