1import { Observable } from '../Observable'; 2import { async } from '../scheduler/async'; 3import { SchedulerAction, SchedulerLike } from '../types'; 4import { isNumeric } from '../util/isNumeric'; 5import { Subscriber } from '../Subscriber'; 6 7/** 8 * Creates an Observable that emits sequential numbers every specified 9 * interval of time, on a specified {@link SchedulerLike}. 10 * 11 * <span class="informal">Emits incremental numbers periodically in time. 12 * </span> 13 * 14 * ![](interval.png) 15 * 16 * `interval` returns an Observable that emits an infinite sequence of 17 * ascending integers, with a constant interval of time of your choosing 18 * between those emissions. The first emission is not sent immediately, but 19 * only after the first period has passed. By default, this operator uses the 20 * `async` {@link SchedulerLike} to provide a notion of time, but you may pass any 21 * {@link SchedulerLike} to it. 22 * 23 * ## Example 24 * Emits ascending numbers, one every second (1000ms) up to the number 3 25 * ```ts 26 * import { interval } from 'rxjs'; 27 * import { take } from 'rxjs/operators'; 28 * 29 * const numbers = interval(1000); 30 * 31 * const takeFourNumbers = numbers.pipe(take(4)); 32 * 33 * takeFourNumbers.subscribe(x => console.log('Next: ', x)); 34 * 35 * // Logs: 36 * // Next: 0 37 * // Next: 1 38 * // Next: 2 39 * // Next: 3 40 * ``` 41 * 42 * @see {@link timer} 43 * @see {@link delay} 44 * 45 * @param {number} [period=0] The interval size in milliseconds (by default) 46 * or the time unit determined by the scheduler's clock. 47 * @param {SchedulerLike} [scheduler=async] The {@link SchedulerLike} to use for scheduling 48 * the emission of values, and providing a notion of "time". 49 * @return {Observable} An Observable that emits a sequential number each time 50 * interval. 51 * @static true 52 * @name interval 53 * @owner Observable 54 */ 55export function interval(period = 0, 56 scheduler: SchedulerLike = async): Observable<number> { 57 if (!isNumeric(period) || period < 0) { 58 period = 0; 59 } 60 61 if (!scheduler || typeof scheduler.schedule !== 'function') { 62 scheduler = async; 63 } 64 65 return new Observable<number>(subscriber => { 66 subscriber.add( 67 scheduler.schedule(dispatch, period, { subscriber, counter: 0, period }) 68 ); 69 return subscriber; 70 }); 71} 72 73function dispatch(this: SchedulerAction<IntervalState>, state: IntervalState) { 74 const { subscriber, counter, period } = state; 75 subscriber.next(counter); 76 this.schedule({ subscriber, counter: counter + 1, period }, period); 77} 78 79interface IntervalState { 80 subscriber: Subscriber<number>; 81 counter: number; 82 period: number; 83} 84