Rules
prefer-is-nullish
Treat null and undefined uniformly unless the distinction is intentional.
Purpose and behavior
Treat null and undefined uniformly unless the distinction is intentional.
Reports Predicate.isNull, isNotNull, isUndefined and isNotUndefined calls. Prefer isNullish/isNotNullish. If a boundary must distinguish null and undefined, suppress with an explicit reason instead of weakening the shared policy.
Options
No configurable options. Enable with "rules/prefer-is-nullish": "error".
Invalid example
if (Predicate.isNull(x)) {}Valid example
if (Predicate.isNullish(x)) {}Fixes and exceptions
This rule reports diagnostics without an automatic fix. Rewrite the code deliberately rather than guessing its intended semantics.
For a genuine boundary exception, use an oxlint-disable-next-line rules/prefer-is-nullish -- reason comment. Examples illustrate this rule alone and may omit imports and declarations.
Source and tests
Enabled by the Effect preset.