Rule proposal: prefer-nullish-coalescing

[fisker]

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Nullish_coalescing_operator

https://github.com/tc39/proposal-nullish-coalescing

let foo = (undefined || null) || bar;

// equals

let foo = (undefined || null) ?? bar;

anyway, it not safe for foo || bar -> foo ?? bar, we should use ESLint suggestion api

[sindresorhus]

For inspiration: https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/prefer-nullish-coalescing.md

This obviously has to wait until ESLint supports ??.

[EvgenyOrekhov]

Support for nullish coalescing operator was added in ESLint 7.2.0.

[sindresorhus]

This is now accepted. PR welcome.

[sindresorhus]

If anyone wants to work on this, see the initial attempt and feedback in #1388.