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121 lines
2.4 KiB
Markdown
121 lines
2.4 KiB
Markdown
# JavaScript Reducers
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If any additional arguments were passed, fx converts them into a function which
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takes the JSON as an argument named `x`.
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By default, fx uses builtin JavaScript VM ([goja](https://github.com/dop251/goja)),
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but also can be used with node.
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```sh
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export FX_LANG=js # Default
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```
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Or for usage with node:
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```sh
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export FX_LANG=node
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```
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An example of anonymous function used as a reducer:
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```sh
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$ echo '{"foo": [{"bar": "value"}]}' | fx 'x => x.foo[0].bar'
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value
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```
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The same reducer function can be simplified to:
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```sh
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$ echo '{"foo": [{"bar": "value"}]}' | fx 'x.foo[0].bar'
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value
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```
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Each argument treated as a reducer function.
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```sh
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$ echo '{"foo": [{"bar": "value"}]}' | fx 'x.foo' 'x[0]' 'x.bar'
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value
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```
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Update JSON using the spread operator:
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```sh
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$ echo '{"name": "fx", "count": 0}' | fx '{...this, count: 1}'
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{
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"name": "fx",
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"count": 1
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}
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```
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## Dot
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Fx supports simple JS-like syntax for accessing data, which can be used with any `FX_LANG`.
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```sh
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$ echo '{"foo": [{"bar": "value"}]}' | fx .foo[0].bar
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value
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```
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## .fxrc.js
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Create _.fxrc.js_ file in `$HOME` directory, and define some useful functions.
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```js
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// .fxrc.js
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function upper(s) {
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return s.toUpperCase()
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}
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```
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```sh
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$ cat data.json | fx .name upper
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ANTON
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```
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## Node
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```sh
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export FX_LANG=node
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```
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Use any npm package by installing it globally. Create _.fxrc.js_ file in `$HOME`
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directory, and require any packages or define global functions. For example,
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to access all lodash methods without `_` prefix, put next line into your
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_.fxrc.js_ file:
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```js
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Object.assign(global, require('lodash/fp'))
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```
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And now you will be able to call all lodash methods. For example, see who's been
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committing to react recently:
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```sh
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curl 'https://api.github.com/repos/facebook/react/commits?per_page=100' \
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| fx 'groupBy("commit.author.name")' 'mapValues(size)' toPairs 'sortBy(1)' reverse 'take(10)' fromPairs
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```
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> To be able to require global modules make sure you have correct `NODE_PATH` env variable.
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> ```sh
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> export NODE_PATH=`npm root -g`
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> ```
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The _.fxrc.js_ file supports both: `import` and `require`.
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```js
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// .fxrc.js
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import 'zx/globals'
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const _ = require('lodash')
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```
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> If you want to use _.fxrc.js_ for both `FX_LANG=js` and `FX_LANG=node`,
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> separate parts by `// nodejs:` comment:
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> ```js
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> // .fxrc.js
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> function upper(s) {
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> return s.toUpperCase()
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> }
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> // nodejs:
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> import 'zx/globals'
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> const _ = require('lodash')
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> ```
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