144 lines
2.6 KiB
Markdown
144 lines
2.6 KiB
Markdown
# @babel/plugin-proposal-decorators
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> Compile class and object decorators to ES5
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## Example
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(examples are from proposal)
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### Simple class decorator
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```js
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@annotation
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class MyClass { }
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function annotation(target) {
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target.annotated = true;
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}
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```
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### Class decorator
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```js
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@isTestable(true)
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class MyClass { }
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function isTestable(value) {
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return function decorator(target) {
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target.isTestable = value;
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}
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}
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```
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### Class function decorator
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```js
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class C {
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@enumerable(false)
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method() { }
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}
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function enumerable(value) {
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return function (target, key, descriptor) {
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descriptor.enumerable = value;
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return descriptor;
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}
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}
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```
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## Installation
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```sh
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npm install --save-dev @babel/plugin-proposal-decorators
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```
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## Usage
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Add the following line to your .babelrc file:
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```json
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{
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"plugins": ["@babel/plugin-proposal-decorators"]
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}
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```
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### Via CLI
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```sh
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babel --plugins @babel/plugin-proposal-decorators script.js
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```
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### Via Node API
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```javascript
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require("@babel/core").transform("code", {
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plugins: ["@babel/plugin-proposal-decorators"]
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});
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```
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## Options
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### `decoratorsBeforeExport`
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`boolean`, defaults to `true`.
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```js
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// decoratorsBeforeExport: true
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@decorator
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export class Foo {}
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// decoratorsBeforeExport: false
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export @decorator class Bar {}
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```
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This option was added to help tc39 collect feedback from the community by allowing experimentation with both possible syntaxes.
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For more information, check out: [tc39/proposal-decorators#69](https://github.com/tc39/proposal-decorators/issues/69).
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### `legacy`
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`boolean`, defaults to `false`.
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Use the legacy (stage 1) decorators syntax and behavior.
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#### NOTE: Compatibility with `@babel/plugin-proposal-class-properties`
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If you are including your plugins manually and using `@babel/plugin-proposal-class-properties`, make sure that `@babel/plugin-proposal-decorators` comes *before* `@babel/plugin-proposal-class-properties`.
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When using the `legacy: true` mode, `@babel/plugin-proposal-class-properties` must be used in `loose` mode to support the `@babel/plugin-proposal-decorators`.
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Wrong:
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```json
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{
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"plugins": [
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"@babel/plugin-proposal-class-properties",
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"@babel/plugin-proposal-decorators"
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]
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}
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```
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Right:
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```json
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{
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"plugins": [
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"@babel/plugin-proposal-decorators",
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"@babel/plugin-proposal-class-properties"
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]
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}
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```
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```json
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{
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"plugins": [
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["@babel/plugin-proposal-decorators", { "legacy": true }],
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["@babel/plugin-proposal-class-properties", { "loose" : true }]
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]
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}
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```
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## References
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* [Proposal: JavaScript Decorators](https://github.com/wycats/javascript-decorators/blob/master/README.md)
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