babel-plugin-transform-es2015-duplicate-keys

What is babel-plugin-transform-es2015-duplicate-keys?

The babel-plugin-transform-es2015-duplicate-keys npm package is designed to transform duplicate keys in object literals to valid ES2015 (also known as ES6) syntax. This is particularly useful when you are working with code that needs to be compatible with ES2015 standards, as duplicate keys in object literals were handled differently in ES5 and earlier versions. This plugin ensures that your code adheres to the latest standards, avoiding potential issues in environments that strictly follow ES2015+ specifications.

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

Transforming Duplicate Keys

This feature automatically transforms objects with duplicate keys in your JavaScript code. For example, if you have an object literal with two 'foo' keys, each with different types or values, this plugin will help ensure that the object is transformed in a way that is compatible with ES2015 standards. The exact transformation depends on the plugin's implementation details and the JavaScript engine's handling of such cases.

{"type": "object", "properties": {"foo": {"type": "number"}, "foo": {"type": "string"}}}

Other packages similar to babel-plugin-transform-es2015-duplicate-keys

@babel/plugin-transform-duplicate-keys

This package serves a similar purpose to babel-plugin-transform-es2015-duplicate-keys by transforming duplicate keys in object literals to be compatible with the latest JavaScript standards. The main difference lies in the scope of the transformation, as it might be updated to support versions beyond ES2015, offering broader compatibility and potentially more features.

babel-plugin-check-es2015-constants

While not directly related to transforming duplicate keys, this package complements the functionality by checking and transforming ES2015 constants. It ensures that 'const' declarations do not change value, which aligns with the goal of writing code that adheres to ES2015 standards. It's a useful tool in the broader context of code transformation for ES2015 compatibility.

README

babel-plugin-transform-es2015-duplicate-keys

Compile objects with duplicate keys to valid strict ES5.

This plugin actually converts duplicate keys in objects to be computed properties, which then must be handled by the transform-es2015-computed-properties plugin. The final result won't contain any object literals with duplicate keys.

Example

In

var x = { a: 5, a: 6 };
var y = {
  get a() {},
  set a(x) {},
  a: 3
};

Out

var x = { a: 5, ["a"]: 6 };
var y = {
  get a() {},
  set a(x) {},
  ["a"]: 3
};

Installation

npm install --save-dev babel-plugin-transform-es2015-duplicate-keys

Usage

Via .babelrc (Recommended)

.babelrc

{
  "plugins": ["transform-es2015-duplicate-keys"]
}

Via CLI

babel --plugins transform-es2015-duplicate-keys script.js

Via Node API

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