Edit

@babel/plugin-transform-computed-properties

NOTE: This plugin is included in @babel/preset-env

Example

In

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

Out

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

Usage

With a configuration file (Recommended)

Without options:

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

With options:

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

Via CLI

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

Via Node API

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.

⚠️ Consider migrating to the top level setComputedProperties assumption.

// babel.config.json
{
  "assumptions": {
    "setComputedProperties": true
  }
}

Example

In

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

Out

When setComputedProperties is true.

var _obj;

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

When setComputedProperties is false.

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);

You can read more about configuring plugin options here

← classesdestructuring →