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/Babel 7

@babel/plugin-proposal-optional-chaining

NOTE: This plugin is included in @babel/preset-env, in ES2020

Example​

Accessing deeply nested properties​ 

const obj = {
  foo: {
    bar: {
      baz: 42,
    },
  },
};

const baz = obj?.foo?.bar?.baz; // 42

const safe = obj?.qux?.baz; // undefined

// Optional chaining and normal chaining can be intermixed
obj?.foo.bar?.baz; // Only access `foo` if `obj` exists, and `baz` if
// `bar` exists

// Example usage with bracket notation:
obj?.["foo"]?.bar?.baz; // 42

Calling deeply nested functions​ 

const obj = {
  foo: {
    bar: {
      baz() {
        return 42;
      },
    },
  },
};

const baz = obj?.foo?.bar?.baz(); // 42

const safe = obj?.qux?.baz(); // undefined
const safe2 = obj?.foo.bar.qux?.(); // undefined

const willThrow = obj?.foo.bar.qux(); // Error: not a function

// Top function can be called directly, too.
function test() {
  return 42;
}
test?.(); // 42

exists?.(); // undefined

Constructing deeply nested classes​ 

const obj = {
  foo: {
    bar: {
      baz: class {
      },
    },
  },
};

const baz = new obj?.foo?.bar?.baz(); // baz instance

const safe = new obj?.qux?.baz(); // undefined
const safe2 = new obj?.foo.bar.qux?.(); // undefined

const willThrow = new obj?.foo.bar.qux(); // Error: not a constructor

// Top classes can be called directly, too.
class Test {
}
new Test?.(); // test instance

new exists?.(); // undefined

Deleting deeply nested properties​

Added in: v7.8.0

const obj = {
  foo: {
    bar: {},
  },
};

const ret = delete obj?.foo?.bar?.baz; // true

Installation​

  • npm
  • Yarn
  • pnpm
npm install --save-dev @babel/plugin-proposal-optional-chaining

Usage​ 

{
  "plugins": ["@babel/plugin-proposal-optional-chaining"]
}

Via CLI​ 

babel --plugins @babel/plugin-proposal-optional-chaining script.js

Via Node API​ 

require("@babel/core").transformSync("code", {
  plugins: ["@babel/plugin-proposal-optional-chaining"],
});

Options​

loose​

boolean, defaults to false.

When true, this transform will pretend document.all does not exist, and perform loose equality checks with null instead of strict equality checks against both null and undefined.

⚠️ Consider migrating to the top level noDocumentAll assumption.

{
  "assumptions": {
    "noDocumentAll": true
  }
}

Example​

In

foo?.bar;

Out (noDocumentAll === true)

foo == null ? void 0 : foo.bar;

Out (noDocumentAll === false)

foo === null || foo === void 0 ? void 0 : foo.bar;

You can read more about configuring plugin options here

References​

© 2014-present Sebastian McKenzie
Licensed under the MIT License.
https://babeljs.io/docs/babel-plugin-proposal-optional-chaining/