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- import { Observable } from '../Observable';
- import { SchedulerLike } from '../types';
- import { async as asyncScheduler } from '../scheduler/async';
- import { isScheduler } from '../util/isScheduler';
- import { isValidDate } from '../util/isDate';
- /**
- * Creates an observable that will wait for a specified time period, or exact date, before
- * emitting the number 0.
- *
- * <span class="informal">Used to emit a notification after a delay.</span>
- *
- * This observable is useful for creating delays in code, or racing against other values
- * for ad-hoc timeouts.
- *
- * The `delay` is specified by default in milliseconds, however providing a custom scheduler could
- * create a different behavior.
- *
- * ## Examples
- *
- * Wait 3 seconds and start another observable
- *
- * You might want to use `timer` to delay subscription to an
- * observable by a set amount of time. Here we use a timer with
- * {@link concatMapTo} or {@link concatMap} in order to wait
- * a few seconds and start a subscription to a source.
- *
- * ```ts
- * import { of, timer, concatMap } from 'rxjs';
- *
- * // This could be any observable
- * const source = of(1, 2, 3);
- *
- * timer(3000)
- * .pipe(concatMap(() => source))
- * .subscribe(console.log);
- * ```
- *
- * Take all values until the start of the next minute
- *
- * Using a `Date` as the trigger for the first emission, you can
- * do things like wait until midnight to fire an event, or in this case,
- * wait until a new minute starts (chosen so the example wouldn't take
- * too long to run) in order to stop watching a stream. Leveraging
- * {@link takeUntil}.
- *
- * ```ts
- * import { interval, takeUntil, timer } from 'rxjs';
- *
- * // Build a Date object that marks the
- * // next minute.
- * const currentDate = new Date();
- * const startOfNextMinute = new Date(
- * currentDate.getFullYear(),
- * currentDate.getMonth(),
- * currentDate.getDate(),
- * currentDate.getHours(),
- * currentDate.getMinutes() + 1
- * );
- *
- * // This could be any observable stream
- * const source = interval(1000);
- *
- * const result = source.pipe(
- * takeUntil(timer(startOfNextMinute))
- * );
- *
- * result.subscribe(console.log);
- * ```
- *
- * ### Known Limitations
- *
- * - The {@link asyncScheduler} uses `setTimeout` which has limitations for how far in the future it can be scheduled.
- *
- * - If a `scheduler` is provided that returns a timestamp other than an epoch from `now()`, and
- * a `Date` object is passed to the `dueTime` argument, the calculation for when the first emission
- * should occur will be incorrect. In this case, it would be best to do your own calculations
- * ahead of time, and pass a `number` in as the `dueTime`.
- *
- * @param due If a `number`, the amount of time in milliseconds to wait before emitting.
- * If a `Date`, the exact time at which to emit.
- * @param scheduler The scheduler to use to schedule the delay. Defaults to {@link asyncScheduler}.
- */
- export function timer(due: number | Date, scheduler?: SchedulerLike): Observable<0>;
- /**
- * Creates an observable that starts an interval after a specified delay, emitting incrementing numbers -- starting at `0` --
- * on each interval after words.
- *
- * The `delay` and `intervalDuration` are specified by default in milliseconds, however providing a custom scheduler could
- * create a different behavior.
- *
- * ## Example
- *
- * ### Start an interval that starts right away
- *
- * Since {@link interval} waits for the passed delay before starting,
- * sometimes that's not ideal. You may want to start an interval immediately.
- * `timer` works well for this. Here we have both side-by-side so you can
- * see them in comparison.
- *
- * Note that this observable will never complete.
- *
- * ```ts
- * import { timer, interval } from 'rxjs';
- *
- * timer(0, 1000).subscribe(n => console.log('timer', n));
- * interval(1000).subscribe(n => console.log('interval', n));
- * ```
- *
- * ### Known Limitations
- *
- * - The {@link asyncScheduler} uses `setTimeout` which has limitations for how far in the future it can be scheduled.
- *
- * - If a `scheduler` is provided that returns a timestamp other than an epoch from `now()`, and
- * a `Date` object is passed to the `dueTime` argument, the calculation for when the first emission
- * should occur will be incorrect. In this case, it would be best to do your own calculations
- * ahead of time, and pass a `number` in as the `startDue`.
- * @param startDue If a `number`, is the time to wait before starting the interval.
- * If a `Date`, is the exact time at which to start the interval.
- * @param intervalDuration The delay between each value emitted in the interval. Passing a
- * negative number here will result in immediate completion after the first value is emitted, as though
- * no `intervalDuration` was passed at all.
- * @param scheduler The scheduler to use to schedule the delay. Defaults to {@link asyncScheduler}.
- */
- export function timer(startDue: number | Date, intervalDuration: number, scheduler?: SchedulerLike): Observable<number>;
- /**
- * @deprecated The signature allowing `undefined` to be passed for `intervalDuration` will be removed in v8. Use the `timer(dueTime, scheduler?)` signature instead.
- */
- export function timer(dueTime: number | Date, unused: undefined, scheduler?: SchedulerLike): Observable<0>;
- export function timer(
- dueTime: number | Date = 0,
- intervalOrScheduler?: number | SchedulerLike,
- scheduler: SchedulerLike = asyncScheduler
- ): Observable<number> {
- // Since negative intervalDuration is treated as though no
- // interval was specified at all, we start with a negative number.
- let intervalDuration = -1;
- if (intervalOrScheduler != null) {
- // If we have a second argument, and it's a scheduler,
- // override the scheduler we had defaulted. Otherwise,
- // it must be an interval.
- if (isScheduler(intervalOrScheduler)) {
- scheduler = intervalOrScheduler;
- } else {
- // Note that this *could* be negative, in which case
- // it's like not passing an intervalDuration at all.
- intervalDuration = intervalOrScheduler;
- }
- }
- return new Observable((subscriber) => {
- // If a valid date is passed, calculate how long to wait before
- // executing the first value... otherwise, if it's a number just schedule
- // that many milliseconds (or scheduler-specified unit size) in the future.
- let due = isValidDate(dueTime) ? +dueTime - scheduler!.now() : dueTime;
- if (due < 0) {
- // Ensure we don't schedule in the future.
- due = 0;
- }
- // The incrementing value we emit.
- let n = 0;
- // Start the timer.
- return scheduler.schedule(function () {
- if (!subscriber.closed) {
- // Emit the next value and increment.
- subscriber.next(n++);
- if (0 <= intervalDuration) {
- // If we have a interval after the initial timer,
- // reschedule with the period.
- this.schedule(undefined, intervalDuration);
- } else {
- // We didn't have an interval. So just complete.
- subscriber.complete();
- }
- }
- }, due);
- });
- }
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