@babel/plugin-transform-block-scoping
Advanced tools
Compile ES2015 block scoping (const and let) to ES5
The @babel/plugin-transform-block-scoping npm package is a Babel plugin that transforms JavaScript code to convert block scoping (let and const) to function scoping (var) where necessary. This is particularly useful for ensuring compatibility with older environments that do not support ES6 block-scoped variables.
Transform let and const to var
This feature transforms block-scoped variables (let and const) into function-scoped variables (var) to ensure compatibility with older JavaScript engines.
if (true) {
let x = 'hello';
}
// Transformed to:
if (true) {
var x = 'hello';
}Block scoping for loops
This feature correctly scopes the loop variable within closures, preventing common errors when using setTimeout or similar asynchronous functions within loops.
for (let i = 0; i < 3; i++) {
setTimeout(function() { console.log(i); }, 0);
}
// Transformed to:
for (var i = 0; i < 3; i++) {
(function(i) {
setTimeout(function() { console.log(i); }, 0);
})(i);
}This package is a predecessor to @babel/plugin-transform-block-scoping and offers similar functionality, transforming ES2015 block-scoped variables to ES5. It is now deprecated in favor of the @babel suite of plugins.
While not a direct alternative, fast-async is a Babel plugin that transforms async/await and generators to ES5, including handling block scoping within async functions. It provides a different set of features but deals with modern JavaScript syntax transformation like @babel/plugin-transform-block-scoping.
babel-preset-env is a Babel preset that includes @babel/plugin-transform-block-scoping among other plugins. It automatically determines the Babel plugins and polyfills you need based on your supported environments. It's a more comprehensive solution that includes similar functionality.
Compile ES2015 block scoping (const and let) to ES5
See our website @babel/plugin-transform-block-scoping for more information.
Using npm:
npm install --save-dev @babel/plugin-transform-block-scoping
or using yarn:
yarn add @babel/plugin-transform-block-scoping --dev
v7.27.1 (2025-04-30)
babel-parser
babel-parser, babel-types
babel-plugin-proposal-destructuring-private, babel-plugin-proposal-do-expressions, babel-traverse
babel-helper-wrap-function, babel-plugin-transform-async-to-generator
babel-helper-remap-async-to-generator, babel-plugin-transform-async-to-generator
babel-helper-fixtures, babel-parser
babel-generator, babel-parser
babel-parser
babel-compat-data, babel-preset-env
babel-traverse
babel-generator
babel-plugin-bugfix-v8-spread-parameters-in-optional-chaining, babel-plugin-proposal-decorators, babel-plugin-transform-arrow-functions, babel-plugin-transform-class-properties, babel-plugin-transform-destructuring, babel-plugin-transform-object-rest-spread, babel-plugin-transform-optional-chaining, babel-plugin-transform-parameters, babel-traverse
babel-runtime-corejs2, babel-runtime-corejs3, babel-runtime
regenerator-runtime dep in @babel/runtime (@nicolo-ribaudo)babel-compat-data, babel-preset-env
babel-compat-data, babel-standalone
babel-register
@babel/register to cts (@liuxingbaoyu)babel-cli, babel-compat-data, babel-core, babel-generator, babel-helper-compilation-targets, babel-helper-fixtures, babel-helper-module-imports, babel-helper-module-transforms, babel-helper-plugin-test-runner, babel-helper-transform-fixture-test-runner, babel-helpers, babel-node, babel-parser, babel-plugin-transform-modules-amd, babel-plugin-transform-modules-commonjs, babel-plugin-transform-modules-systemjs, babel-plugin-transform-modules-umd, babel-plugin-transform-react-display-name, babel-plugin-transform-regenerator, babel-plugin-transform-runtime, babel-plugin-transform-typeof-symbol, babel-plugin-transform-typescript, babel-preset-env, babel-register, babel-standalone, babel-types
babel-plugin-transform-regenerator
babel-helpers, babel-plugin-transform-async-generator-functions, babel-plugin-transform-regenerator, babel-preset-env, babel-runtime-corejs3
babel-helpers, babel-plugin-transform-regenerator
babel-helpers
babel-helpers, babel-plugin-transform-modules-commonjs, babel-runtime-corejs3
interopRequireWildcard size (@liuxingbaoyu)babel-helpers, babel-plugin-transform-async-generator-functions, babel-plugin-transform-regenerator, babel-preset-env, babel-runtime-corejs3
regeneratorRuntime size (@liuxingbaoyu)FAQs
Compile ES2015 block scoping (const and let) to ES5
The npm package @babel/plugin-transform-block-scoping receives a total of 22,847,713 weekly downloads. As such, @babel/plugin-transform-block-scoping popularity was classified as popular.
We found that @babel/plugin-transform-block-scoping demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 4 open source maintainers collaborating on the project.
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