https://github.com/kosich/babel-plugin-partial-expressions
https://github.com/kosich/babel-plugin-partial-expressions
Last synced: 3 months ago
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- Host: GitHub
- URL: https://github.com/kosich/babel-plugin-partial-expressions
- Owner: kosich
- Created: 2021-04-29T12:11:37.000Z (about 4 years ago)
- Default Branch: main
- Last Pushed: 2021-05-14T20:02:46.000Z (about 4 years ago)
- Last Synced: 2025-03-11T18:05:54.980Z (3 months ago)
- Language: JavaScript
- Size: 670 KB
- Stars: 0
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# Partial Expressions - Babel plugin
Try it in this **[babel playground](https://babeljs.io/repl#?browsers=defaults%2C%20not%20ie%2011%2C%20not%20ie_mob%2011&build=&builtIns=usage&corejs=3.6&spec=false&loose=false&code_lz=DYUwLgBAlgdgxhAvBAfhA-hA1BAjAbgCg4B7GAZxNADpgSBzACljkYBZcBKTow0SAA5QBIACZIIbAAwQAPgD4M2CACYipClRC0GjISNE8gA&debug=false&forceAllTransforms=false&shippedProposals=false&circleciRepo=&evaluate=false&fileSize=false&timeTravel=false&sourceType=module&lineWrap=false&presets=stage-0%2Cstage-1&prettier=false&targets=&version=7.13.17&externalPlugins=%40kosich%2Fbabel-plugin-partial-expressions-experiment%400.0.4)**.
Or install it via
```
npm i @kosich/babel-plugin-partial-expressions-experiment -D
```
And then add it to your `babel.config.json` as [described here](https://babeljs.io/docs/en/plugins).
_NOTE: put it before pipeline operator plugins, if you use those._
## About
Partial expressions is a syntax sugar to simplify writing expression that are awating one additional variable.
Syntax:
- `_` is a placeholder for the value
- `~` is used to mark partial expression root and is required whenever we use `_` (except for RHS pipes)
Examples:
```js
let bang = ~ _ + '!';
// equals to
let bang = x => x + '!';
```
As a partially applied function:
```js
let bangLog = ~ console.log(_, '!');
// equals to
let bangLog = x => console.log(x, '!');
```
And as a context of application:
```js
let toBase16 = ~ _.toString(16);
// equals to
let toBase16 = x => x.toString(16);
```
It is also compatible with the [pipeline operator](https://github.com/tc39/proposal-pipeline-operator):
I tried to cover a special case for **pipes**, when `_` is in RHS of a pipe. E.g:
```js
let value = 42 |> _ + 1 |> console.log;
// equals to
let value = 42 |> (x => x + 1) |> console.log;
```
Similarly, we can do partial application:
```js
42 |> console.log(_, '!');
// equals to
42 |> (x => console.log(x, '!'));
```
And as a context:
```js
42 |> _.toString(16) |> _.toUpperCase();
// equals to
42 |> (x => x.toString(16)) |> (x => x.toUpperCase());
```
## Rules
1. Expression is considered partial if an unbound `_` symbol is used in it.
2. Expression boudaries are limited by following:
2.1 `~` operator
`let a = ~ _ + '!'` equals `let a = x => x + '!'`
2.2 RHS in pipeline operator
`42 |> _ + 1 |> console.log` equals `42 |> (x => x + 1) |> console.log`
## The End 🙂