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This commit is contained in:
Sven SAULEAU
2018-06-04 16:32:39 +02:00
committed by Henry Zhu
parent b6eaaa2496
commit b445b79734
143 changed files with 1286 additions and 11238 deletions
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packages/babel-plugin-proposal-optional-chaining/README.md
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# @babel/plugin-proposal-optional-chaining
The Optional Chaining Operator allows you to handle properties of deeply nested
objects without worrying about undefined intermediate objects.
> Transform optional chaining operators into a series of nil checks
## Example
See our website [@babel/plugin-proposal-optional-chaining](https://new.babeljs.io/docs/en/next/babel-plugin-proposal-optional-chaining.html) for more information.
### Accessing deeply nested properties
## Install
```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
Using npm:
```sh
npm install --save-dev @babel/plugin-proposal-optional-chaining
npm install --save @babel/plugin-proposal-optional-chaining
```
## Usage
### Via `.babelrc` (Recommended)
**.babelrc**
```json
{
"plugins": ["@babel/plugin-proposal-optional-chaining"]
}
```
### Via CLI
or using yarn:
```sh
babel --plugins @babel/plugin-proposal-optional-chaining script.js
yarn add --save @babel/plugin-proposal-optional-chaining
```
### Via Node API
```javascript
require("@babel/core").transform("code", {
plugins: ["@babel/plugin-proposal-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)