* 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)'

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

Start interactive mode without passing any arguments:

$ curl ... | fx

Click on fields to expand or collapse JSON tree, use mouse wheel to scroll view. To select text, press alt or option key.

Next commands available in interactive mode:

Key	Command
q or Esc or Ctrl+c	Exit
e/E	Expand/Collapse all
up/down or k/j	Scroll up/down one line
g/G	Goto top/bottom

Related

• jq – cli JSON processor on C
• jl – functional sed for JSON on Haskell
• xx – fx-like JSON tool (go)
• ymlx - fx-like YAML cli processor
• jv – interactive JSON viewer (go)
• jid – interactive cli tool based on jq (go)

License

MIT