> For the complete documentation index, see [llms.txt](https://soufatn.gitbook.io/rxjs-book/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://soufatn.gitbook.io/rxjs-book/summary/schedulers/virtual_scheduler.md).

# Rx.VirtualTimeScheduler

Base class for providing scheduling in virtual time. This inherits from the `Rx.Scheduler` class.

## Usage #\#

The following shows an example of using the `Rx.VirtualTimeScheduler`. In order for this to work, you must implement the `add`, `toDateTimeOffset` and `toRelative` methods as described below.

```javascript
/* Comparer required for scheduling priority */
function comparer (x, y) {
    if (x > y) { return 1; }
    if (x < y) { return -1; }
    return 0;
}

var scheduler = new Rx.VirtualTimeScheduler(0, comparer);

/**
 * Adds a relative time value to an absolute time value.
 * @param {Any} absolute Absolute virtual time value.
 * @param {Any} relative Relative virtual time value to add.
 * @return {Any} Resulting absolute virtual time sum value.
 */
scheduler.add = function (absolute, relative) {
    return absolute + relative;
};

/**
 * Converts an absolute time to a number
 * @param {Number} The absolute time in ms
 * @returns {Number} The absolute time in ms
 */
scheduler.toDateTimeOffset = function (absolute) {
    return new Date(absolute).getTime();
};

/**
 * Converts the time span number/Date to a relative virtual time value.
 * @param {Number} timeSpan TimeSpan value to convert.
 * @return {Number} Corresponding relative virtual time value.
 */
scheduler.toRelative = function (timeSpan) {
    return timeSpan;
};

// Schedule some time
scheduler.scheduleAbsolute(1, function () { console.log('foo'); });
scheduler.scheduleAbsolute(2, function () { console.log('bar'); });
scheduler.scheduleAbsolute(3, function () { scheduler.stop(); });

// Start the scheduler
scheduler.start();

// => foo
// => bar

// Check the clock once stopped
console.log(scheduler.now());
// => 3

console.log(scheduler.clock);
// => 3
```

### Location

* rx.virtualtime.js

## `VirtualTimeScheduler Constructor` #\#

* [`constructor`](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvirtualtimeschedulerinitialclock-comparer)

## `VirtualTimeScheduler Instance Methods` #\#

* [`advanceBy`](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvirtualtimeschedulerprototypeadvancebytime)
* [`advanceTo`](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvirtualtimeschedulerprototypeadvancetotime)
* [`scheduleAbsolute`](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvirtualtimeschedulerprototypescheduleabsoluteduetime-action)
* [`scheduleAbsoluteWithState`](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvirtualtimeschedulerprototypescheduleabsolutewithstatestate-duetime-action)
* [`scheduleRelative`](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvirtualtimeschedulerprototypeschedulerelativeduetime-action)
* [`scheduleRelativeWithState`](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvirtualtimeschedulerprototypeschedulerelativewithstatestate-duetime-action)
* [`sleep`](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvirtualtimeschedulerprototypesleeptime)
* [`start`](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvritualtimeschedulerprototypestart)
* [`stop`](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvritualtimeschedulerprototypestop)

## `VirtualTimeScheduler Instance Properties` #\#

* [`isEnabled`](/rxjs-book/summary/schedulers/virtual_scheduler.md#isenabled)

## `VirtualTimeScheduler Protected Abstract Methods` #\#

* [`add`](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvirtualtimeschedulerprototypeaddabsolute-relative)
* [`toDateTimeOffset`](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvirtualtimeschedulerprototypetodatetimeoffsetabsolute)
* [`toRelative`](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvirtualtimeschedulerprototypetorelativetimespan)

## `VirtualTimeScheduler Protected Methods` #\#

* [`getNext`](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvirtualtimeschedulerprototypegetnext)

## Inherited Classes #\#

* [`Rx.Scheduler`](https://github.com/Reactive-Extensions/RxJS/blob/master/doc/api/schedulers/scheduler.md)

## *VirtualTimeScheduler Constructor* #\#

### `Rx.VirtualTimeScheduler(initialClock, comparer)` <a href="#rxvirtualtimescheduler" id="rxvirtualtimescheduler"></a>

[#](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvirtualtimescheduler) [Ⓢ](https://github.com/Reactive-Extensions/RxJS/blob/master/src/core/concurrency/virtualtimescheduler.js#L38-L44)

Creates a new virtual time scheduler with the specified initial clock value and absolute time comparer.

#### Arguments

1. `initialClock` *(Function)*: Initial value for the clock.
2. `comparer` *(Function)*: Comparer to determine causality of events based on absolute time.

#### Example

```javascript
function comparer (x, y) {
    if (x > y) { return 1; }
    if (x < y) { return -1; }
    return 0;
}

var scheduler = new Rx.VirtualTimeScheduler(
    0,          /* initial clock of 0 */
    comparer    /* comparer for determining order */
);
```

### Location

* rx.virtualtime.js

## *VirtualTimeScheduler Instance Methods* #\#

### `Rx.VirtualTimeScheduler.prototype.advanceBy(time)` <a href="#rxvirtualtimeschedulerprototypeadvancebytime" id="rxvirtualtimeschedulerprototypeadvancebytime"></a>

[#](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvirtualtimeschedulerprototypeadvancebytime) [Ⓢ](https://github.com/Reactive-Extensions/RxJS/blob/master/src/core/concurrency/virtualtimescheduler.js#L166-L176)

Advances the scheduler's clock by the specified relative time, running all work scheduled for that timespan.

#### Arguments

1. `time` *(Any)*: Relative time to advance the scheduler's clock by.

#### Example

```javascript
var scheduler = new MyVirtualScheduler(
    200 /* initial time */
);

scheduler.scheduleAbsolute(250, function () {
    console.log('hello');
});

scheduler.advanceBy(300);
// => hello

console.log(scheduler.clock);
// => 500
```

### Location

* rx.virtualtime.js

### `Rx.VirtualTimeScheduler.prototype.advanceTo(time)` <a href="#rxvirtualtimeschedulerprototypeadvancetotime" id="rxvirtualtimeschedulerprototypeadvancetotime"></a>

[#](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvirtualtimeschedulerprototypeadvancetotime) [Ⓢ](https://github.com/Reactive-Extensions/RxJS/blob/master/src/core/concurrency/virtualtimescheduler.js#L136-L160)

Advances the scheduler's clock to the specified time, running all work till that point.

#### Arguments

1. `time` *(Any)*: Absolute time to advance the scheduler's clock to.

#### Example

```javascript
var scheduler = new MyVirtualScheduler(
    0 /* initial time */
);

scheduler.scheduleAbsolute(100, function () {
    console.log('hello');
});

scheduler.scheduleAbsolute(200, function () {
    console.log('world');
});

scheduler.advanceBy(300);
// => hello
// => world

console.log(scheduler.clock);
// => 300
```

### Location

* rx.virtualtime.js

### `Rx.VirtualTimeScheduler.prototype.scheduleAbsolute(dueTime, action)` <a href="#rxvirtualtimeschedulerprototypescheduleabsoluteduetime-action" id="rxvirtualtimeschedulerprototypescheduleabsoluteduetime-action"></a>

[#](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvirtualtimeschedulerprototypescheduleabsoluteduetime-action) [Ⓢ](https://github.com/Reactive-Extensions/RxJS/blob/master/src/core/concurrency/virtualtimescheduler.js#L216-L218)

Schedules an action to be executed at dueTime.

#### Arguments

1. `dueTime` *(Any)*: Absolute time at which to execute the action.
2. `action` *(Function)*: Action to be executed.

#### Returns

*(Disposable)*: The disposable object used to cancel the scheduled action (best effort).

#### Example

```javascript
var scheduler = new MyVirtualScheduler(
    0 /* initial time */
);

scheduler.scheduleAbsolute(100, function () {
    console.log('hello');
});

scheduler.scheduleAbsolute(200, function () {
    console.log('world');
});

scheduler.advanceBy(300);
// => hello
// => world

console.log(scheduler.clock);
// => 300
```

### Location

* rx.virtualtime.js

### `Rx.VirtualTimeScheduler.prototype.scheduleAbsoluteWithState(state, dueTime, action)` <a href="#rxvirtualtimeschedulerprototypescheduleabsolutewithstatestate-duetime-action" id="rxvirtualtimeschedulerprototypescheduleabsolutewithstatestate-duetime-action"></a>

[#](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvirtualtimeschedulerprototypescheduleabsolutewithstatestate-duetime-action) [Ⓢ](https://github.com/Reactive-Extensions/RxJS/blob/master/src/core/concurrency/virtualtimescheduler.js#L227-L236)

Schedules an action to be executed at dueTime.

#### Arguments

1. `state`: *(Any)*: State passed to the action to be executed.
2. `dueTime` *(Any)*: Absolute time at which to execute the action.
3. `action` *(Function)*: Action to be executed.

#### Returns

*(Disposable)*: The disposable object used to cancel the scheduled action (best effort).

#### Example

```javascript
var scheduler = new MyVirtualScheduler(
    0 /* initial time */
);

scheduler.scheduleAbsoluteWithState('world', 100, function (x) {
    console.log('hello ' + x);
});

scheduler.scheduleAbsoluteWithState(200, function () {
    console.log('goodnight ' + x);
}, 'moon');

scheduler.start();
// => hello world
// => goodnight moon

console.log(scheduler.clock);
// => 200
```

### Location

* rx.virtualtime.js

### `Rx.VirtualTimeScheduler.prototype.scheduleRelative(dueTime, action)` <a href="#rxvirtualtimeschedulerprototypeschedulerelativeduetime-action" id="rxvirtualtimeschedulerprototypeschedulerelativeduetime-action"></a>

[#](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvirtualtimeschedulerprototypeschedulerelativeduetime-action) [Ⓢ](https://github.com/Reactive-Extensions/RxJS/blob/master/src/core/concurrency/virtualtimescheduler.js#L100-L102)

Schedules an action to be executed at dueTime.

#### Arguments

1. `dueTime` *(Any)*: Relative time after which to execute the action.
2. `action` *(Function)*: Action to be executed.

#### Returns

*(Disposable)*: The disposable object used to cancel the scheduled action (best effort).

#### Example

```javascript
var scheduler = new MyVirtualScheduler(
    100 /* initial time */
);

scheduler.scheduleRelative(100, function () {
    console.log('hello');
});

scheduler.scheduleRelative(200, function () {
    console.log('world');
});

scheduler.start();
// => hello
// => world

console.log(scheduler.clock);
// => 400
```

### Location

* rx.virtualtime.js

### `Rx.VirtualTimeScheduler.prototype.scheduleRelativeWithState(state, dueTime, action)` <a href="#rxvirtualtimeschedulerprototypeschedulerelativewithstatestate-duetime-action" id="rxvirtualtimeschedulerprototypeschedulerelativewithstatestate-duetime-action"></a>

[#](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvirtualtimeschedulerprototypeschedulerelativewithstatestate-duetime-action) [Ⓢ](https://github.com/Reactive-Extensions/RxJS/blob/master/src/core/concurrency/virtualtimescheduler.js#L89-L92)

Schedules an action to be executed at dueTime.

#### Arguments

1. `state`: *(Any)*: State passed to the action to be executed.
2. `dueTime` *(Any)*: Relative time after which to execute the action.
3. `action` *(Function)*: Action to be executed.

#### Returns

*(Disposable)*: The disposable object used to cancel the scheduled action (best effort).

#### Example

```javascript
var scheduler = new MyVirtualScheduler(
    0 /* initial time */
);

scheduler.scheduleRelativeWithState('world', 100, function (x) {
    console.log('hello ' + x);
});

scheduler.scheduleRelativeWithState('moon', 200, function () {
    console.log('goodnight ' + x);
});

scheduler.start();
// => hello world
// => goodnight moon

console.log(scheduler.clock);
// => 300
```

### Location

* rx.virtualtime.js

### `Rx.VirtualTimeScheduler.prototype.sleep(time)` <a href="#rxvritualtimeschedulerprototypesleeptime" id="rxvritualtimeschedulerprototypesleeptime"></a>

[#](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvritualtimeschedulerprototypesleeptime) [Ⓢ](https://github.com/Reactive-Extensions/RxJS/blob/master/src/core/concurrency/virtualtimescheduler.js#L182-L190)

Advances the scheduler's clock by the specified relative time.

#### Arguments

1. `time` *(Any)*: Relative time to advance the scheduler's clock by.

#### Example

```javascript
var scheduler = new MyVirtualScheduler(
    0 /* initial time */
);

scheduler.sleep(400);

console.log(scheduler.clock);
// => 400
```

### Location

* rx.virtualtime.js

### `Rx.VirtualTimeScheduler.prototype.start()` <a href="#rxvritualtimeschedulerprototypestart" id="rxvritualtimeschedulerprototypestart"></a>

[#](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvritualtimeschedulerprototypestart) [Ⓢ](https://github.com/Reactive-Extensions/RxJS/blob/master/src/core/concurrency/virtualtimescheduler.js#L107-L123)

Starts the virtual time scheduler.

#### Example

```javascript
var scheduler = new MyVirtualScheduler(
    0 /* initial time */
);

scheduler.scheduleRelativeWithState('world', 100, function (x) {
    console.log('hello ' + x);
});

scheduler.scheduleRelativeWithState('moon', 200, function () {
    console.log('goodnight ' + x);
});

scheduler.start();
// => hello world
// => goodnight moon

console.log(scheduler.clock);
// => 400
```

### Location

* rx.virtualtime.js

### `Rx.VirtualTimeScheduler.prototype.stop()` <a href="#rxvritualtimeschedulerprototypestop" id="rxvritualtimeschedulerprototypestop"></a>

[#](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvritualtimeschedulerprototypestop) [Ⓢ](https://github.com/Reactive-Extensions/RxJS/blob/master/src/core/concurrency/virtualtimescheduler.js#L128-L130)

Stops the virtual time scheduler.

#### Example

```javascript
var scheduler = new MyVirtualScheduler(
    0 /* initial time */
);

scheduler.scheduleRelative(100, function () {
    console.log('hello world');
});

scheduler.scheduleRelative(100, function () {
    scheduler.stop();
});

scheduler.scheduleRelative(100, function () {
    console.log('hello world');
});

scheduler.start();
// => hello world
```

### Location

* rx.virtualtime.js

## *VirtualTimeScheduler Abstract Protected Methods* #\#

### `Rx.VirtualTimeScheduler.prototype.add(absolute, relative)` <a href="#rxvirtualtimeschedulerprototypeaddabsolute-relative" id="rxvirtualtimeschedulerprototypeaddabsolute-relative"></a>

[#](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvirtualtimeschedulerprototypeaddabsolute-relative) [Ⓢ](https://github.com/Reactive-Extensions/RxJS/blob/master/src/core/subjects/asyncsubject.js#L54)

Adds a relative time value to an absolute time value. This method is used in several methods including `scheduleRelativeWithState`, `advanceBy` and `sleep`.

### Arguments

1. `absolute` *(Any)*: Absolute virtual time value.
2. `relative` *(Any)*: Relative virtual time value.

#### Returns

*(Any)*: Resulting absolute virtual time sum value.

#### Example

One possible implementation could be as simple as the following:

```javascript
scheduler.add = function (absolute, relative) {
    return absolute + relative;
};
```

### Location

* rx.virtualtime.js

### `Rx.VirtualTimeScheduler.prototype.toDateTimeOffset(absolute)` <a href="#rxvirtualtimeschedulerprototypetodatetimeoffsetabsolute" id="rxvirtualtimeschedulerprototypetodatetimeoffsetabsolute"></a>

[#](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvirtualtimeschedulerprototypetodatetimeoffsetabsolute) [Ⓢ](https://github.com/Reactive-Extensions/RxJS/blob/master/src/core/subjects/asyncsubject.js#L61)

Converts an absolute time to a number. This is used directly in the `now` method on the `Rx.Scheduler`

### Arguments

1. `absolute` *(Any)*: The absolute time to convert.

#### Returns

*(Number)*: The absolute time in ms.

#### Example

One possible implementation could be as simple as the following:

```javascript
// String -> Number
scheduler.toDateTimeOffset = function (absolute) {
    return return absolute.length;
};
```

### Location

* rx.virtualtime.js

### `Rx.VirtualTimeScheduler.prototype.toRelative(timeSpan)` <a href="#rxvirtualtimeschedulerprototypetorelativetimespan" id="rxvirtualtimeschedulerprototypetorelativetimespan"></a>

[#](/rxjs-book/summary/schedulers/virtual_scheduler.md#rxvirtualtimeschedulerprototypetorelativetimespan) [Ⓢ](https://github.com/Reactive-Extensions/RxJS/blob/master/src/core/subjects/asyncsubject.js#L61)

Converts the time span number/Date to a relative virtual time value.

### Arguments

1. `timeSpan` *(Any)*: The time span number value to convert.  This is used directly in `scheduleWithRelativeAndState` and `scheduleWithAbsoluteAndState`.

#### Returns

*(Number)*: Corresponding relative virtual time value.

#### Example

One possible implementation could be as simple as the following:

```javascript
// Number -> Number
scheduler.toRelative = function (timeSpan) {
    return timeSpan;
};
```

### Location

* rx.virtualtime.js