prefer-map-has

Prefer Map.has over Map.get when only key presence is observed

Comparing Map.get with undefined retrieves a value only to determine whether its key exists.
Instead, you SHOULD call Map.has when the mapped value cannot itself be undefined.

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

Reported

function contains(values: Map<string, int32>, key: string): boolean {
    return values.get(key) !== undefined;
}
Accepted

function contains(values: Map<string, int32>, key: string): boolean {
    return values.has(key);
}
Prior art

- eslint-plugin-unicorn · prefer-has-check

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