https://github.com/sam-parsons/babel-plugin-transform-walrus-operator

return a value from an assignment expression
https://github.com/sam-parsons/babel-plugin-transform-walrus-operator

babel babel-plugin walrus-operator

Last synced: about 2 months ago
JSON representation

return a value from an assignment expression

• Host: GitHub
• URL: https://github.com/sam-parsons/babel-plugin-transform-walrus-operator
• Owner: sam-parsons
• Created: 2021-03-14T22:35:02.000Z (almost 4 years ago)
• Default Branch: main
• Last Pushed: 2022-03-29T22:10:23.000Z (almost 3 years ago)
• Last Synced: 2024-11-16T16:48:11.984Z (about 2 months ago)
• Topics: babel, babel-plugin, walrus-operator
• Language: JavaScript
• Homepage: https://www.npmjs.com/package/babel-plugin-transform-walrus-operator
• Size: 231 KB
• Stars: 3
• Watchers: 1
• Forks: 0
• Open Issues: 2
• Metadata Files:
  • Readme: README.md

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# babel-plugin-transform-walrus-operator

> compile the walrus operator ```:=``` to an IIFE

## About

assignment statement

- assigns 42 to x

- returns undefined

```js

x = 42;

```

assignment expression

- assigns 42 to x

- returns 42

```js

(x := 42)

```



#### Example use case

```js

y = func(x);

const arr = [y, y ** 2, y ** 4, y ** 6];

``` 

can become

```js

const arr = [y := func(x), y ** 2, y ** 4, y ** 6]

``` 



#### Transformation

```js

if (x := 2) alert();

```

generally becomes

```js

if ((function (x) {

  if (typeof x === 'undefined') throw new Error();

  x = 2;

  return x;

})(x)) alert();

```

## Babel Setup

this plugin relies upon the ```:=``` token, it will have to be manually added to babel's parser

follow Tan Li Hau's guide, you will fork babel and add a token to the parser.  see my babel fork commit

## Installation

```sh

$ npm install --save-dev babel-plugin-transform-walrus-operator

```

## Usage

### Via `.babelrc` (Recommended)

**.babelrc**

```json

{

  "plugins": ["transform-walrus-operator"]

}

```

### Via CLI

```sh

$ babel --plugins transform-walrus-operator script.js

```

### Via Node API

```javascript

require('babel-core').transform('code', {

  plugins: ['transform-walrus-operator'],

});

```

# License

MIT