59 lines
845 B
Markdown
59 lines
845 B
Markdown
# @babel/plugin-check-constants
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> Validate ES2015 constants (prevents reassignment of const variables).
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## Example
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**In**
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```js
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const a = 1;
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a = 2;
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```
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**Out**
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```bash
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repl: "a" is read-only
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1 | const a = 1;
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> 2 | a = 2;
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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-check-constants
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```
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## Usage
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### Via `.babelrc` (Recommended)
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**.babelrc**
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```json
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{
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"plugins": ["@babel/check-constants"]
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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/check-constants 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/check-constants"]
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});
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```
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## Note
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This check will only validate consts. If you need it to compile down to `var` then you must also install and enable [`transform-block-scoping`](http://babeljs.io/docs/plugins/transform-block-scoping/).
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