window.md

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Rx.Observable.prototype.window()

Ⓢ

The window method periodically subdivide items from an Observable into Observable windows and emit these windows rather than emitting the items one at a time.

Window is similar to buffer, but rather than emitting packets of items from the original Observable, it emits Observables, each one of which emits a subset of items from the original Observable and then terminates with an onCompleted call.

Like buffer, window has many varieties, each with its own way of subdividing the original Observable into the resulting Observable emissions, each one of which contains a "window" onto the original emitted items. In the terminology of the window method, when a window "opens," this means that a new Observable is emitted and that Observable will begin emitting items emitted by the source Observable. When a window "closes," this means that the emitted Observable stops emitting items from the source Observable and calls its Subscribers' onCompleted method and terminates.

With window closing selector

Rx.Observable.prototype.window(windowClosingSelector);

This version of window opens its first window immediately. It closes the currently open window and immediately opens a new one each time it observes an object emitted by the Observable that is returned from windowClosingSelector. In this way, this version of window emits a series of non-overlapping windows whose collective onNext emissions correspond one-to-one with those of the source Observable.

Arguments

1. windowClosingSelector (Function): A function invoked to define the closing of each produced window.

Returns

(Observable): An observable sequence of windows.

Example

// With closings
var source = Rx.Observable.timer(0, 50)
  .window(function () { return Rx.Observable.timer(125); })
  .take(3)
  .flatMap(function (x) { return x.toArray(); });

var subscription = source.subscribe(
  function (x) {
    console.log('Next: %s', x);
  },
  function (err) {
    console.log('Error: %s', err);
  },
  function () {
    console.log('Completed');
  });

  // => Next: 0,1,2
  // => Next: 3,4,5
  // => Next: 6,7
  // => Completed

With window opening and window closing selector

Rx.Observable.prototype.window(windowOpenings, windowClosingSelector);

This version of window opens a window whenever it observes the windowOpenings Observable emit an Opening object and at the same time calls windowClosingSelector to generate a closing Observable associated with that window. When that closing Observable emits an object, window closes that window. Since the closing of currently open windows and the opening of new windows are activities that are regulated by independent Observables, this version of window may create windows that overlap (duplicating items from the source Observable) or that leave gaps (discarding items from the source Observable).

Arguments

1. windowOpenings (Observable): Observable sequence whose elements denote the creation of new windows
2. windowClosingSelector (Function): A function invoked to define the closing of each produced window.

Returns

(Observable): An observable sequence of windows.

Example

/* Using Openings and Closing Selector */
var openings = Rx.Observable.interval(200);

var source = Rx.Observable.interval(50)
  .window(openings, function (x) { return Rx.Observable.timer(x + 100); })
  .take(3);

var subscription = source.subscribe(
  function (x) {
    console.log('Next: %s', x);
  },
  function (err) {
    console.log('Error: %s', err);
  },
  function () {
    console.log('Completed');
  });

// => Next: 3,4
// => Next: 7,8
// => Next: 11,12
// => Completed

With boundaries

Rx.Observable.prototype.window(windowBoundaries);

This version of window returns an Observable that emits non-overlapping buffered items from the source Observable each time the specified boundary Observable emits an item.

Arguments

1. windowBoundaries (Observable): Sequence of window boundary markers. The current window is closed and a new window is opened upon receiving a boundary marker.

Returns

(Observable): An observable sequence of windows.

Example

/* With window boundaries */
var openings = Rx.Observable.interval(500);

// Convert the window to an array
var source = Rx.Observable.timer(0, 100)
  .window(openings)
  .take(3)
  .flatMap(function (x) { return x.toArray(); });

var subscription = source.subscribe(
  function (x) {
    console.log('Next: %s', x);
  },
  function (err) {
    console.log('Error: %s', err);
  },
  function () {
    console.log('Completed');
  });

// => Next: 0,1,2,3,4
// => Next: 5,6,7,8,9,10
// => Next: 11,12,13,14,15
// => Completed

Location

File:

• /src/core/linq/observable/window.js

Dist:

• rx.all.js
• rx.all.compat.js
• rx.coincidence.js

Prerequisites:

• rx.js | rx.compat.js | rx.lite.js | rx.lite.compat.js

NPM Packages:

• rx

NuGet Packages:

• RxJS-All
• RxJS-Coincidence

Unit Tests:

• /tests/observable/window.js