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https://github.com/gwmccull/babel-plugin-transform-optional-chaining
Manual copy of the babel-plugin-transform-optional-chaining sub-module
https://github.com/gwmccull/babel-plugin-transform-optional-chaining
Last synced: 2 months ago
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Manual copy of the babel-plugin-transform-optional-chaining sub-module
- Host: GitHub
- URL: https://github.com/gwmccull/babel-plugin-transform-optional-chaining
- Owner: gwmccull
- Created: 2017-10-26T00:08:57.000Z (about 7 years ago)
- Default Branch: master
- Last Pushed: 2017-10-26T16:53:13.000Z (about 7 years ago)
- Last Synced: 2024-08-03T09:09:43.536Z (6 months ago)
- Language: JavaScript
- Size: 1.95 KB
- Stars: 13
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
- awesome-github-star - babel-plugin-transform-optional-chaining - plugin-transform-optional-chaining sub-module | gwmccull | 13 | (JavaScript)
README
# @babel/plugin-transform-optional-chaining
The Optional Chaining Operator allows you to handle properties of deeply nested
objects without worrying about undefined intermediate objects.
## Example
### Accessing deeply nested properties
```js
const obj = {
foo: {
bar: {
baz: 42,
},
},
};
const baz = obj?.foo?.bar?.baz; // 42
const safe = obj?.qux?.baz; // undefined
// Optional chaining and normal chaining can be intermixed
obj?.foo.bar?.baz; // Only access `foo` if `obj` exists, and `baz` if
// `bar` exists
```
### Calling deeply nested functions
```js
const obj = {
foo: {
bar: {
baz() {
return 42;
},
},
},
};
const baz = obj?.foo?.bar?.baz(); // 42
const safe = obj?.qux?.baz(); // undefined
const safe2 = obj?.foo.bar.qux?.(); // undefined
const willThrow = obj?.foo.bar.qux(); // Error: not a function
// Top function can be called directly, too.
function test() {
return 42;
}
test?.(); // 42
exists?.(); // undefined
```
### Constructing deeply nested classes
```js
const obj = {
foo: {
bar: {
baz: class {
},
},
},
};
const baz = new obj?.foo?.bar?.baz(); // baz instance
const safe = new obj?.qux?.baz(); // undefined
const safe2 = new obj?.foo.bar.qux?.(); // undefined
const willThrow = new obj?.foo.bar.qux(); // Error: not a constructor
// Top classes can be called directly, too.
class Test {
}
new Test?.(); // test instance
new exists?.(); // undefined
```
## Installation
```sh
npm install --save-dev @babel/plugin-transform-optional-chaining
```
## Usage
### Via `.babelrc` (Recommended)
**.babelrc**
```json
{
"plugins": ["transform-optional-chaining"]
}
```
### Via CLI
```sh
babel --plugins transform-optional-chaining script.js
```
### Via Node API
```javascript
require("@babel/core").transform("code", {
plugins: ["transform-optional-chaining"]
});
```
## Options
### `loose`
`boolean`, defaults to `false`.
When `true`, this transform will pretend `document.all` does not exist,
and perform loose equality checks with `null` instead of string equality checks
against both `null` and `undefined`.
#### Example
In
```javascript
foo?.bar;
```
Out (`loose === true`)
```javascript
foo == null ? void 0 : foo.bar;
```
Out (`loose === false`)
```javascript
foo === null || foo === void 0 ? void 0 : foo.bar;
```
## References
* [Proposal: Optional Chaining](https://github.com/tc39/proposal-optional-chaining)