fx/README.md

<p align="center"><img src="https://user-images.githubusercontent.com/141232/35405308-4b41f446-0238-11e8-86c1-21f407cc8460.png" height="100" alt="fx"></p>
<p align="center"><img src="https://user-images.githubusercontent.com/141232/47933350-f0f22900-df06-11e8-9cf2-88492c1be774.gif" width="530" alt="fx example"></p>

_* Function eXecution_

# [![Build Status](https://travis-ci.org/antonmedv/fx.svg?branch=master)](https://travis-ci.org/antonmedv/fx)

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](https://github.com/antonmedv/fx/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](https://github.com/sebmarkbage/ecmascript-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](https://github.com/stedolan/jq) – cli JSON processor on C
* [jl](https://github.com/chrisdone/jl) – functional sed for JSON on Haskell
* [xx](https://github.com/antonmedv/xx) – `fx`-like JSON tool (*go*)
* [ymlx](https://github.com/matthewadams/ymlx) - `fx`-like YAML cli processor
* [jv](https://github.com/maxzender/jv) – interactive JSON viewer (*go*)
* [jid](https://github.com/simeji/jid) – interactive cli tool based on jq (*go*)

## License

MIT