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- # babel-plugin-transform-es2015-block-scoping
- > Compile ES2015 block scoping (const and let) to ES5
- ## Installation
- ```sh
- npm install --save-dev babel-plugin-transform-es2015-block-scoping
- ```
- ## Usage
- ### Via `.babelrc` (Recommended)
- **.babelrc**
- Without options:
- ```json
- {
- "plugins": ["transform-es2015-block-scoping"]
- }
- ```
- With options:
- ```json
- {
- "plugins": [
- ["transform-es2015-block-scoping", {
- "throwIfClosureRequired": true
- }]
- ]
- }
- ```
- ### Via CLI
- ```sh
- babel --plugins transform-es2015-block-scoping script.js
- ```
- ### Via Node API
- ```javascript
- require("babel-core").transform("code", {
- plugins: ["transform-es2015-block-scoping"]
- });
- ```
- ## Options `throwIfClosureRequired`
- In cases such as the following it's impossible to rewrite let/const without adding an additional function and closure while transforming:
- ```javascript
- for (let i = 0; i < 5; i++) {
- setTimeout(() => console.log(i), 1);
- }
- ```
- In extremely performance-sensitive code, this can be undesirable. If `"throwIfClosureRequired": true` is set, Babel throws when transforming these patterns instead of automatically adding an additional function.
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