@rxjs-ninja/rxjs-utility/lib/map-if.d.ts

Useful utilities for RxJS

/**
 * @packageDocumentation
 * @module Utility
 */
import { MapFn, PredicateFn } from '../types/utility';
import { OperatorFunction } from 'rxjs';
/**
 * Returns an Observable that emits the value from either the `trueResult` or `falseResult` based on the result from
 * the source with a [[PredicateFn]].
 *
 * @category Mapping
 *
 * @remarks Each method can return it's own type which you should handle in later operators
 *
 * @typeParam I The type of value from the source
 * @typeParam T The type returned from the Truthy result
 * @typeParam F The type returned from the Falsy result
 *
 * @param predicate The method to check the value from the source Observable
 * @param trueResult The method with return value for a truthy [[PredicateFn]]
 * @param falseResult The method with return value for a falsy [[PredicateFn]]
 *
 * @example
 * Returns a FizzBuzz based on the input value
 * ```ts
 * const input = [ 1, 2, 3, 4, 5, 6, 10, 15, 16 ];
 * from(input).pipe(
 *  mapIf<number, string, number>(
 *    (value) => value % 15 == 0 || value % 3 == 0 || value % 5 == 0,
 *    (value) => (value % 15 == 0 ? `FizzBuzz` : value % 3 === 0 ? 'Fizz' : 'Buzz'),
 *    (value) => value,
 *  ),
 * ).subscribe();
 * ```
 * Output: `1, 2, 'Fizz', 4, 'Buzz', 'Fizz', 10, 'FizzBuzz', 16`
 *
 * @returns Observable that emits a value from the truthy or falsy [[MapFn]] based on the [[PredicateFn]] result
 */
export declare function mapIf<I extends unknown, T = I | unknown, F = I | unknown>(predicate: PredicateFn<I>, trueResult: MapFn<I, T>, falseResult: MapFn<I, F>): OperatorFunction<I, T | F>;