????
Your IP : 3.128.199.33
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);
});
}