prefer-map-keys-values

Prefer Map.keys or Map.values when one entry component is unused

Iterating Map.entries constructs key-value pairs even when one component is never used.
Instead, you SHOULD iterate Map.keys or Map.values directly.

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

Reported

function copy(values: Map<string, int32>, output: int32[]): void {
    for (const (_, value) of values.entries()) {
        output.push(value);
    }
}
Accepted

function copy(values: Map<string, int32>, output: int32[]): void {
    for (const value of values.values()) {
        output.push(value);
    }
}
Prior art

- Clippy · forkvmap

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