fx/doc/js.md

JavaScript Reducers

If any additional arguments were passed, fx converts them into a function which takes the JSON as an argument named x.

By default, fx uses builtin JavaScript VM (goja), but also can be used with node.

export FX_LANG=js # Default

Or for usage with node:

export FX_LANG=node

An example of anonymous function used as a reducer:

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

The same reducer function can be simplified to:

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

Each argument treated as a reducer function.

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

Update JSON using the spread operator:

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

Dot

Fx supports simple JS-like syntax for accessing data, which can be used with any FX_LANG.

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

.fxrc.js

Create .fxrc.js file in $HOME directory, and define some useful functions.

// .fxrc.js
function upper(s) {
  return s.toUpperCase()
}

$ cat data.json | fx .name upper
ANTON

Node

export FX_LANG=node

Use any npm package by installing it globally. Create .fxrc.js file in $HOME directory, and require any packages or define global functions. For example, to access all lodash methods without _ prefix, put next line into your .fxrc.js file:

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

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 'groupBy("commit.author.name")' 'mapValues(size)' toPairs 'sortBy(1)' reverse 'take(10)' fromPairs

To be able to require global modules make sure you have correct NODE_PATH env variable.

export NODE_PATH=`npm root -g`

The .fxrc.js file supports both: import and require.

// .fxrc.js
import 'zx/globals'
const _ = require('lodash')

If you want to use .fxrc.js for both FX_LANG=js and FX_LANG=node, separate parts by // nodejs: comment:

// .fxrc.js
function upper(s) {
  return s.toUpperCase()
}
// nodejs:
import 'zx/globals'
const _ = require('lodash')