What is @babel/plugin-transform-duplicate-keys?
The @babel/plugin-transform-duplicate-keys npm package is designed to help developers manage object literals in JavaScript that have duplicate keys. When using this plugin, Babel will transform object literals containing duplicate keys by ensuring that the last key-value pair is the one that is ultimately defined, following the standard JavaScript behavior. This can be particularly useful in scenarios where code is being generated or transformed and duplicate keys may be introduced unintentionally.
What are @babel/plugin-transform-duplicate-keys's main functionalities?
Transforming Duplicate Keys in Object Literals
This feature allows the transformation of object literals with duplicate keys in JavaScript code. The plugin ensures that if an object literal contains duplicate keys, only the last occurrence of the key is kept, and previous ones are ignored. This aligns with the standard JavaScript behavior where the last property assignment overrides earlier assignments with the same key.
{"type": "object", "properties": {"duplicateKey": {"type": "string"}, "duplicateKey": {"type": "number"}}}
0
@babel/plugin-transform-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 @babel/plugin-transform-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-duplicate-keys
Usage
Via .babelrc
(Recommended)
.babelrc
{
"plugins": ["@babel/plugin-transform-duplicate-keys"]
}
Via CLI
babel --plugins @babel/plugin-transform-duplicate-keys script.js
Via Node API
require("@babel/core").transform("code", {
plugins: ["@babel/plugin-transform-duplicate-keys"]
});