babel-plugin-transform-es2015-parameters

What is babel-plugin-transform-es2015-parameters?

The babel-plugin-transform-es2015-parameters package is a Babel plugin that transforms ES2015 (ES6) parameter features to ES5. This includes default parameters, rest parameters, and destructuring in function parameters.

What are babel-plugin-transform-es2015-parameters's main functionalities?

Default Parameters

This feature allows you to set default values for function parameters. If no argument is provided for the parameter, the default value is used.

function greet(name = 'World') { console.log('Hello ' + name); } greet(); // Hello World greet('Alice'); // Hello Alice

Rest Parameters

Rest parameters allow you to represent an indefinite number of arguments as an array. This is useful for functions that need to handle a variable number of arguments.

function sum(...numbers) { return numbers.reduce((acc, num) => acc + num, 0); } console.log(sum(1, 2, 3)); // 6

Destructuring in Parameters

Destructuring in function parameters allows you to unpack values from objects or arrays directly in the parameter list. This can make your code more readable and concise.

function printCoordinates({ x, y }) { console.log(`X: ${x}, Y: ${y}`); } printCoordinates({ x: 10, y: 20 }); // X: 10, Y: 20

Other packages similar to babel-plugin-transform-es2015-parameters

babel-plugin-transform-es2015-destructuring

This package transforms ES2015 destructuring syntax to ES5. It focuses specifically on destructuring assignments and function parameters, similar to the destructuring feature in babel-plugin-transform-es2015-parameters.

babel-plugin-transform-es2015-spread

This package transforms ES2015 spread syntax to ES5. While it focuses on spread operations, it complements the rest parameters feature of babel-plugin-transform-es2015-parameters by handling array and object spread.

babel-plugin-transform-es2015-function-name

This package ensures that function names are correctly assigned in ES2015. It is not directly related to parameters but is often used alongside parameter transformation plugins to ensure function names are preserved.

README

babel-plugin-transform-es2015-parameters

Compile ES2015 default and rest parameters to ES5

This plugin transforms ES2015 parameters to ES5, this includes:

• Destructuring parameters
• Default parameters
• Rest parameters

Examples

In

function test(x = "hello", { a, b }, ...args) {
  console.log(x, a, b, args);
}

Out

function test() {
  var x = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : "hello";
  var _ref = arguments[1];
  var a = _ref.a,
      b = _ref.b;

  for (var _len = arguments.length, args = Array(_len > 2 ? _len - 2 : 0), _key = 2; _key < _len; _key++) {
    args[_key - 2] = arguments[_key];
  }

  console.log(x, a, b, args);
}

Installation

npm install --save-dev babel-plugin-transform-es2015-parameters

Caveats

Default parameters desugar into let declarations to retain proper semantics. If this is not supported in your environment then you'll need the transform-block-scoping plugin.

Usage

Via .babelrc (Recommended)

.babelrc

{
  "plugins": ["transform-es2015-parameters"]
}

Via CLI

babel --plugins transform-es2015-parameters script.js

Via Node API

require("babel-core").transform("code", {
  plugins: ["transform-es2015-parameters"]
});