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107 lines
2.8 KiB
107 lines
2.8 KiB
# eslint-visitor-keys |
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[](https://www.npmjs.com/package/eslint-visitor-keys) |
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[](http://www.npmtrends.com/eslint-visitor-keys) |
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[](https://travis-ci.org/eslint/eslint-visitor-keys) |
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[](https://david-dm.org/eslint/eslint-visitor-keys) |
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Constants and utilities about visitor keys to traverse AST. |
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## 💿 Installation |
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Use [npm] to install. |
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```bash |
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$ npm install eslint-visitor-keys |
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``` |
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### Requirements |
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- [Node.js] `^12.22.0`, `^14.17.0`, or `>=16.0.0` |
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## 📖 Usage |
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To use in an ESM file: |
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```js |
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import * as evk from "eslint-visitor-keys" |
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``` |
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To use in a CommonJS file: |
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```js |
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const evk = require("eslint-visitor-keys") |
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``` |
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### evk.KEYS |
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> type: `{ [type: string]: string[] | undefined }` |
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Visitor keys. This keys are frozen. |
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This is an object. Keys are the type of [ESTree] nodes. Their values are an array of property names which have child nodes. |
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For example: |
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``` |
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console.log(evk.KEYS.AssignmentExpression) // → ["left", "right"] |
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``` |
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### evk.getKeys(node) |
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> type: `(node: object) => string[]` |
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Get the visitor keys of a given AST node. |
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This is similar to `Object.keys(node)` of ES Standard, but some keys are excluded: `parent`, `leadingComments`, `trailingComments`, and names which start with `_`. |
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This will be used to traverse unknown nodes. |
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For example: |
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```js |
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const node = { |
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type: "AssignmentExpression", |
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left: { type: "Identifier", name: "foo" }, |
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right: { type: "Literal", value: 0 } |
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} |
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console.log(evk.getKeys(node)) // → ["type", "left", "right"] |
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``` |
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### evk.unionWith(additionalKeys) |
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> type: `(additionalKeys: object) => { [type: string]: string[] | undefined }` |
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Make the union set with `evk.KEYS` and the given keys. |
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- The order of keys is, `additionalKeys` is at first, then `evk.KEYS` is concatenated after that. |
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- It removes duplicated keys as keeping the first one. |
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For example: |
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```js |
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console.log(evk.unionWith({ |
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MethodDefinition: ["decorators"] |
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})) // → { ..., MethodDefinition: ["decorators", "key", "value"], ... } |
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``` |
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## 📰 Change log |
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See [GitHub releases](https://github.com/eslint/eslint-visitor-keys/releases). |
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## 🍻 Contributing |
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Welcome. See [ESLint contribution guidelines](https://eslint.org/docs/developer-guide/contributing/). |
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### Development commands |
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- `npm test` runs tests and measures code coverage. |
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- `npm run lint` checks source codes with ESLint. |
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- `npm run coverage` opens the code coverage report of the previous test with your default browser. |
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- `npm run release` publishes this package to [npm] registory. |
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[npm]: https://www.npmjs.com/ |
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[Node.js]: https://nodejs.org/ |
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[ESTree]: https://github.com/estree/estree
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