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#276 in Parser implementations

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270 downloads per month
Used in 2 crates (via platz-chart-ext)

MIT license



Continuous Integration

This is an implementation of the JsonLogic specification in Rust.

Project Status

We implement 100% of the standard supported operations defined here.

We also implement the ?:, which is not described in that specification but is a direct alias for if.

All operations are tested using our own test suite in Rust as well as the shared tests for all JsonLogic implementations defined here.

We are working on adding new operations with improved type safety, as well as the ability to define functions as JsonLogic. We will communicate with the broader JsonLogic community to see if we can make them part of the standard as we do so.

Being built in Rust, we are able to provide the package in a variety of languages. The table below describes current language support:

Language Available Via
Rust Cargo
JavaScript (as WASM) Node Package via NPM
Python PyPI



To use as a Rust library, add to your Cargo.toml:

jsonlogic-rs = "~0.1"

If you just want to use the commandline jsonlogic binary:

cargo install jsonlogic-rs --features cmdline


You can install JsonLogic using npm or yarn. In NPM:

npm install --save @bestow/jsonlogic-rs

Note that the package is distributed as a node package, so you'll need to use browserify, webpack, or similar to install for the browser.


Supports Python 3.7+.

Wheels are distributed for many platforms, so you can often just run:

pip install jsonlogic-rs

If a wheel does not exist for your system, this will attempt to build the package. In order for the package to build successfully, you MUST have Rust installed on your local system, and cargo MUST be present in your PATH.

See Building below for more details.



use jsonlogic_rs;
use serde_json::{json, from_str, Value};

// You can pass JSON values deserialized with serde straight into apply().
fn main() {
    let data: Value = from_str(r#"{"a": 7}"#)
            json!({"===": [{"var": "a"}, 7]}),


const jsonlogic = require("jsonlogic-rs")

    {"===": [{"var": "a"}, 7]},
    {"a": 7}


import jsonlogic_rs

res = jsonlogic_rs.apply(
    {"===": [{"var": "a"}, 7]},
    {"a": 7}

assert res == True

# If You have serialized JsonLogic and data, the `apply_serialized` method can
# be used instead
res = jsonlogic_rs.apply_serialized(
    '{"===": [{"var": "a"}, 7]}',
    '{"a": 7}'


Parse JSON data with a JsonLogic rule.

When no <data> or <data> is -, read from stdin.

The result is written to stdout as JSON, so multiple calls
can be chained together if desired.

    jsonlogic <logic> [data]

    -h, --help       Prints help information
    -V, --version    Prints version information

    <logic>    A JSON logic string
    <data>     A string of JSON data to parse. May be provided as stdin.

    jsonlogic '{"===": [{"var": "a"}, "foo"]}' '{"a": "foo"}'
    jsonlogic '{"===": [1, 1]}' null
    echo '{"a": "foo"}' | jsonlogic '{"===": [{"var": "a"}, "foo"]}'

Inspired by and conformant with the original JsonLogic (jsonlogic.com).

Run jsonlogic --help the most up-to-date usage.

An example of chaining multiple results:

$ echo '{"a": "a"}' \
    | jsonlogic '{"if": [{"===": [{"var": "a"}, "a"]}, {"result": true}, {"result": false}]}' \
    | jsonlogic '{"if": [{"!!": {"var": "result"}}, "result was true", "result was false"]}'

"result was true"

Using jsonlogic on the cmdline to explore an API:

> curl -s "https://catfact.ninja/facts?limit=5"

{"current_page":1,"data":[{"fact":"The Egyptian Mau is probably the oldest breed of cat. In fact, the breed is so ancient that its name is the Egyptian word for \u201ccat.\u201d","length":132},{"fact":"Julius Ceasar, Henri II, Charles XI, and Napoleon were all afraid of cats.","length":74},{"fact":"Unlike humans, cats cannot detect sweetness which likely explains why they are not drawn to it at all.","length":102},{"fact":"Cats can be taught to walk on a leash, but a lot of time and patience is required to teach them. The younger the cat is, the easier it will be for them to learn.","length":161},{"fact":"Researchers believe the word \u201ctabby\u201d comes from Attabiyah, a neighborhood in Baghdad, Iraq. Tabbies got their name because their striped coats resembled the famous wavy patterns in the silk produced in this city.","length":212}],"first_page_url":"https:\/\/catfact.ninja\/facts?page=1","from":1,"last_page":67,"last_page_url":"https:\/\/catfact.ninja\/facts?page=67","next_page_url":"https:\/\/catfact.ninja\/facts?page=2","path":"https:\/\/catfact.ninja\/facts","per_page":"5","prev_page_url":null,"to":5,"total":332}

> curl -s "https://catfact.ninja/facts?limit=5" | jsonlogic '{"var": "data"}'

[{"fact":"A cat's appetite is the barometer of its health. Any cat that does not eat or drink for more than two days should be taken to a vet.","length":132},{"fact":"Some notable people who disliked cats:  Napoleon Bonaparte, Dwight D. Eisenhower, Hitler.","length":89},{"fact":"During the time of the Spanish Inquisition, Pope Innocent VIII condemned cats as evil and thousands of cats were burned. Unfortunately, the widespread killing of cats led to an explosion of the rat population, which exacerbated the effects of the Black Death.","length":259},{"fact":"A cat has approximately 60 to 80 million olfactory cells (a human has between 5 and 20 million).","length":96},{"fact":"In just seven years, a single pair of cats and their offspring could produce a staggering total of 420,000 kittens.","length":115}]

> curl -s "https://catfact.ninja/facts?limit=5" | jsonlogic '{"var": "data.0"}'

{"fact":"A tiger's stripes are like fingerprints","length":39}

> curl -s "https://catfact.ninja/facts?limit=5" | jsonlogic '{"var": "data.0.fact"}'
"Neutering a male cat will, in almost all cases, stop him from spraying (territorial marking), fighting with other males (at least over females), as well as lengthen his life and improve its quality."

> curl -s "https://catfact.ninja/facts?limit=5" \
    | jsonlogic '{"var": "data.0.fact"}' \
    | jsonlogic '{"in": ["cat", {"var": ""}]}'


> curl -s "https://catfact.ninja/facts?limit=5" \
    | jsonlogic '{"var": "data.0.fact"}' \
    | jsonlogic '{"in": ["cat", {"var": ""}]}' \
    | jsonlogic '{"if": [{"var": ""}, "fact contained cat", "fact did not contain cat"]}'

"fact contained cat"



You must have Rust installed and cargo available in your PATH.

If you would like to build or test the Python distribution, Python 3.7 or newer must be available in your PATH. The venv module must be part of the Python distribution (looking at you, Ubuntu).

If you would like to run tests for the WASM package, node 10 or newer must be available in your PATH.


To build the Rust library, just run cargo build.

You can create a release build with make build.


You can build a debug WASM release with

make debug-wasm

You can build a production WASM release with

make build-wasm

The built WASM package will be in js/. This package is directly importable from node, but needs to be browserified in order to be used in the browser.


To perform a dev install of the Python package, run:

make develop-py

This will automatically create a virtual environment in venv/, install the necessary packages, and then install jsonlogic_rs into that environment.

Note: from our CI experiences, this may not work for Python 3.8 on Windows. If you are running this on a Windows machine and can confirm whether or not this works, let us know!

To build a production source distribution:

make build-py-sdist

To build a wheel (specific to your current system architecture and python version):

make build-py-wheel

The python distribution consists both of the C extension generated from the Rust and a thin wrapper found in py/jsonlogic_rs/. make develop-py will compile the C extension and place it in that directory, where it will be importable by your local venv. When building wheels, the wrapper and the C extension are all packaged together into the resultant wheel, which will be found in dist/. When building an sdist, the Rust extension is not compiled. The Rust and Python source are distributed together in a .tar.gz file, again found in dist/.


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