@babel/plugin-transform-computed-properties

info

This plugin is included in @babel/preset-env

Example

In

JavaScript

var obj = {
  ["x" + foo]: "heh",
  ["y" + bar]: "noo",
  foo: "foo",
  bar: "bar",
};

Out

JavaScript

var _obj;
function _defineProperty(obj, key, value) {
  if (key in obj) {
    Object.defineProperty(obj, key, {
      value: value,
      enumerable: true,
      configurable: true,
      writable: true,
    });
  } else {
    obj[key] = value;
  }
  return obj;
}
var obj = ((_obj = {}),
_defineProperty(_obj, "x" + foo, "heh"),
_defineProperty(_obj, "y" + bar, "noo"),
_defineProperty(_obj, "foo", "foo"),
_defineProperty(_obj, "bar", "bar"),
_obj);

Installation

• npm
• Yarn
• pnpm

npm install --save-dev @babel/plugin-transform-computed-properties

yarn add --dev @babel/plugin-transform-computed-properties

pnpm add --save-dev @babel/plugin-transform-computed-properties

Usage

With a configuration file (Recommended)

Without options:

babel.config.json

{
  "plugins": ["@babel/plugin-transform-computed-properties"]
}

With options:

babel.config.json

{
  "plugins": [
    [
      "@babel/plugin-transform-computed-properties",
      {
        "loose": true
      }
    ]
  ]
}

Via CLI

Shell

babel --plugins @babel/plugin-transform-computed-properties script.js

Via Node API

JavaScript

require("@babel/core").transformSync("code", {
  plugins: ["@babel/plugin-transform-computed-properties"],
});

Options

loose

boolean, defaults to false

Just like method assignment in classes, in loose mode, computed property names use simple assignments instead of being defined. This is unlikely to be an issue in production code.

caution

Consider migrating to the top level setComputedProperties assumption.

babel.config.json

{
  "assumptions": {
    "setComputedProperties": true
  }
}

Example

In

JavaScript

var obj = {
  ["x" + foo]: "heh",
  ["y" + bar]: "noo",
  foo: "foo",
  bar: "bar",
};

Out

When setComputedProperties is true.

JavaScript

var _obj;
var obj = ((_obj = {}),
(_obj["x" + foo] = "heh"),
(_obj["y" + bar] = "noo"),
(_obj.foo = "foo"),
(_obj.bar = "bar"),
_obj);

When setComputedProperties is false.

JavaScript

import _defineProperty from "@babel/runtime/helpers/defineProperty";
var _obj;
var obj = ((_obj = {}),
_defineProperty(_obj, "x" + foo, "heh"),
_defineProperty(_obj, "y" + bar, "noo"),
_defineProperty(_obj, "foo", "foo"),
_defineProperty(_obj, "bar", "bar"),
_obj);

tip

You can read more about configuring plugin options here