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

Usage​

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