manual-filter-map

Prefer filterMap when removing undefined values from a mapped array

Mapping an array before filtering out undefined results allocates an intermediate array.
Instead, you SHOULD call filterMap to keep defined mapped values in one operation.

- Category: performance
- Level: warning
- Fix: suggestion
- Scope: module

Reported

declare const values: (int32 | undefined)[];

const defined = values.map((value) => value).filter((value) => value !== undefined);
Accepted

declare const values: (int32 | undefined)[];

const defined = values.filterMap((value) => value);
Prior art

- Clippy · manualfiltermap

language/linter/src/rules/performance/manualfiltermap.rs:8