eslint-plugin-use-optional-annotation

Disallow undefined for keeping structure.

The following will all be incorrect usage:

const foo = { x: 123, y: undefined };

The following will all be correct usage:

const foo: { x: number, y?: number } = { x: 123 };

We made it to keep this TypeScript styleguide's null-vs-undefined.

https://github.com/basarat/typescript-book/blob/master/docs/styleguide/styleguide.md#null-vs-undefined

Installation

yarn add -D eslint-plugin-use-optional-annotation
# or npm i -D eslint-plugin-use-optional-annotation

Configuration

Set .eslintrc following

plugins: [
  'use-optional-annotation' // add to `plugins` arrays final element.
],
// ...
rules: {
  'use-optional-annotation/use-optional-annotation': 'error'
}