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fx example

* Function eXecution

Command-line JSON processing tool

Features

Don't need to learn new syntax
Plain JavaScript
Formatting and highlighting
Standalone binary
Interactive mode 🎉

Install

$ npm install -g fx

Or download standalone binary from releases page.

Usage

Pipe into fx any JSON and anonymous function for reducing it.

$ echo '{...}' | fx [code ...]

Start interactive mode without passing any arguments:

$ curl ... | fx

Anonymous function

Use an anonymous function as reducer which gets JSON and processes it:

$ echo '{"foo": [{"bar": "value"}]}' | fx 'x => x.foo[0].bar'
value

Binding

If you don't pass anonymous function param => ..., code will be automatically transformed into anonymous function. And you can get access to JSON by this keyword:

$ echo '{"foo": [{"bar": "value"}]}' | fx 'this.foo[0].bar'
value

Dot

It is possible to omit this keyword:

$ echo '{"foo": [{"bar": "value"}]}' | fx .foo[0].bar
value

If single dot is passed, JSON will be processed without modification:

$ echo '{"foo": "bar"}' | fx .
{
  "foo": "bar"
}

Chain

You can pass any number of anonymous functions for reducing JSON:

$ echo '{"foo": [{"bar": "value"}]}' | fx 'x => x.foo' 'this[0]' 'this.bar'
value

Generator

If passed code contains yield keyword, generator expression will be used:

$ curl ... | fx 'for (let user of this) if (user.login.startsWith("a")) yield user'

Access to JSON through this keyword:

$ echo '["a", "b"]' | fx 'yield* this'
[
  "a",
  "b"
]

$ echo '["a", "b"]' | fx 'yield* this; yield "c";'
[
  "a",
  "b",
  "c"
]

Update

You can update existing JSON using spread operator:

$ echo '{"count": 0}' | fx '{...this, count: 1}'
{
  "count": 1
}

Using packages

Use any npm package by installing it globally:

$ npm install -g lodash
$ cat package.json | fx 'require("lodash").keys(this.dependencies)'

Using .fxrc

Create .fxrc file in $HOME directory, and require any packages or define global functions.

For example, access all lodash methods without _ prefix. Put in your .fxrc file:

Object.assign(global, require('lodash'))

And now you will be able to call all lodash methods. For example, see who's been committing to react recently:

curl 'https://api.github.com/repos/facebook/react/commits?per_page=100' \
| fx 'mapValues(groupBy(this, "commit.committer.name"), size)'

To be able require global modules make sure you have correct NODE_PATH env variable.
export NODE_PATH=/usr/local/lib/node_modules

Formatting

If you need something different then JSON (for example arguments for xargs) do not return anything from reducer. undefined value printed into stderr by default.

echo '[]' | fx 'void 0'
undefined

echo '[1,2,3]' | fx 'this.forEach(x => console.log(x))' 2>/dev/null | xargs echo
1 2 3

Other examples

Convert object to array:

$ cat package.json | fx 'Object.keys(this.dependencies)'
[
  "@medv/prettyjson"
]

By the way, fx has shortcut for Object.keys(this). Previous example can be rewritten as:

$ cat package.json | fx this.dependencies ?

Interactive mode