@babel/plugin-transform-parameters

What is @babel/plugin-transform-parameters?

The @babel/plugin-transform-parameters package is a Babel plugin that transforms function parameter features, such as default parameters, destructured parameters, and rest parameters, into ES5-compatible syntax. This transformation allows developers to use modern JavaScript features while maintaining compatibility with older environments that may not support these newer syntaxes natively.

What are @babel/plugin-transform-parameters's main functionalities?

Default Parameters

Transforms functions with default parameters to check for `undefined` and assign a default value if necessary. This allows for cleaner function signatures and easier parameter handling.

function log(message = 'Default message') { console.log(message); }

Destructured Parameters

Enables the use of destructuring in function parameters, transforming it into a series of variable assignments for compatibility. This simplifies the extraction of properties from objects passed as function arguments.

function greet({ name, age }) { console.log(`Hello ${name}, you are ${age} years old.`); }

Rest Parameters

Transforms rest parameters into a standard ES5 arguments pattern, allowing functions to accept an indefinite number of arguments as an array.

function concatenate(separator, ...strings) { return strings.join(separator); }

Other packages similar to @babel/plugin-transform-parameters

@babel/plugin-transform-destructuring

Similar to the destructuring aspect of @babel/plugin-transform-parameters, this plugin transforms destructuring assignments and rest/spread properties to ES5. However, it focuses more broadly on destructuring patterns outside of function parameters as well.

@babel/plugin-transform-spread

This plugin transforms spread elements into a form that can be understood by environments without native support for this syntax. While it deals with the spread operator like the rest parameters feature of @babel/plugin-transform-parameters, it's applied in array literals and function calls rather than function parameters.

README

@babel/plugin-transform-parameters

Compile ES2015 default and rest parameters to ES5

See our website @babel/plugin-transform-parameters for more information.

Install

Using npm:

npm install --save-dev @babel/plugin-transform-parameters

or using yarn:

yarn add @babel/plugin-transform-parameters --dev

Changelog

v7.27.7 (2025-06-26)

:eyeglasses: Spec Compliance

• babel-parser, babel-plugin-transform-classes
  • #17203 Interepret parser allow* options as top level only (@JLHwung)
• babel-parser
  • #17371 fix: disable using in ambient context (@JLHwung)

:bug: Bug Fix

• babel-core
  • #17392 Improve TS babel config loading (@JLHwung)
• babel-types
  • #17376 fix: support negative bigint in valueToNode (@JLHwung)
• babel-plugin-transform-parameters
  • #17352 fix: Params of async function* should throw synchronously (@liuxingbaoyu)

:house: Internal

• babel-plugin-transform-destructuring, babel-plugin-transform-object-rest-spread
  • #17389 Use NodePath#splitExportDeclaration in destructuring transforms (@JLHwung)