collectype / factory/maps/mapKey / mapKeyFactory
mapKeyFactory<
T,C>(ctx,oper): <K>(field,target) =>C
Defined in: factory/maps/mapKey.ts:40
Creates a predicate filter for map key using PredicType.map.key.
T
The item type in the collection.
C extends Wherable<T, C>
The Wherable context type (must extend Wherable<T, C>).
C
The context (usually a collection) supporting the where method.
MapKeyOper
The map key operation (e.g., ‘hasKey’, ‘lacksKey’, etc.).
Returns a function that takes a field (of type Map on T) and a target key, and applies the map key predicate to filter the context.
<
K>(field,target):C
K extends string | number | symbol
K
unknown
C
// Example: Composing a map key filter as a property, homogeneous model
import { BaseFunctions } from 'collectype';
import { mapKeyFactory } from 'collectype';
type Person = { name: string; scores: Map<string, number> };
class PersonFunctions extends BaseFunctions<Person> {
mapHasKey = mapKeyFactory<Person, this>(this, 'hasKey');
}
// Usage:
const people: Person[] = [
{ name: 'Alice', scores: new Map([['math', 18], ['english', 15]]) },
{ name: 'Bob', scores: new Map([['math', 10]]) }
];
const fn = new PersonFunctions(people);
const filtered = fn.mapHasKey('scores', 'english');
// filtered contains the items where 'scores' has the key 'english'