jsq

jsq is a tool for evaluating some JavaScript and printing the result.

Help

Evaluate some JavaScript and print the result

Usage: jsq [OPTIONS] [SCRIPT]

Arguments:
  [SCRIPT]  The JavaScript to be evaluated [default: $]

Options:
  -j, --json-in      Parse input as JSON
  -y, --yaml-in      Parse input as YAML
  -t, --toml-in      Parse input as TOML
  -J, --json-out     Print result as JSON
  -Y, --yaml-out     Print result as YAML
  -T, --toml-out     Print result as TOML
  -N, --no-out       Don't print result
  -f, --file <FILE>  Read SCRIPT from FILE
  -h, --help         Print help
  -V, --version      Print version

Input is avaialable in SCRIPT as $. Environment variables are available in SCRIPT prefixed by $.

Example

Suppose we have some JSON which contains a bunch of superheros and we want to find the hero with the power of "Immortality":

> curl https://mdn.github.io/learning-area/javascript/oojs/json/superheroes.json |
    jsq -jJ '$.members.find(m => m.powers.includes("Immortality"))'
{
  "name": "Eternal Flame",
  "age": 1000000,
  "secretIdentity": "Unknown",
  "powers": [
    "Immortality",
    "Heat Immunity",
    "Inferno",
    "Teleportation",
    "Interdimensional travel"
  ]
}

Semantics

The provided SCRIPT is evaluated by Deno so the Deno runtime and standard library are available, as are third party imports.

$ contains the result of reading STDIN as text, or of parsing it as JSON if the -j flag is set, YAML if the -y flag is set, or TOML if the -t flag is set. If STDIN is a terminal then $ is the empty string.

The value of the final statement in SCRIPT (or undefined if the final statment is not an expression statment) is printed to STDOUT – after being serialized as JSON if the -J flag is set, YAML if the -Y flag is set, or TOML if the -T flag is set – unless the -N flag is set.

Environment variables are available in SCRIPT prefixed by $. e.g. USER is available as $USER.

Why?

JavaScript is a convenient language with which to process JSON (which stands for "JavaScript Object Notation" after all), but the boilerplate of reading from STDIN, parsing, and writing to STDOUT makes many could-be "one-liners" significantly more involved than they need to be. jsq provides a thin wrapper around Deno which handles this boilerplate and makes it more ergonomic to sprinkle a little JavaScript in to a shell script.

jsq can be used for many of the same tasks as jq. A given jq command is often a little shorter than the equivalent jsq command, but if (like the author) you find yourself often forgetting the syntax of jq, and you already know JavaScript, you might find jsq easier to use. To see how jsq compares to jq, check out the translated jq tutorial.

Install

With brew

brew install callum-oakley/tap/jsq

With cargo

Install Deno and then:

cargo install jsq

Binaries

There are binaries for Linux, MacOS, and Windows attached to each release. Install Deno, download a binary, and make it available in your PATH.