scan.md

Rx.Observable.prototype.scan(accumulator, [seed])

Ⓢ

Applies an accumulator function over an observable sequence and returns each intermediate result. The optional seed value is used as the initial accumulator value.

For aggregation behavior with no intermediate results, see Rx.Observable#aggregate or Rx.Observable#reduce.

Arguments

1. accumulator (Function): An accumulator function to be invoked on each element.
2. [seed] (Any): The initial accumulator value.

Returns

(Observable): An observable sequence which results from the comonadic bind operation.

Example

/* Without a seed */
var source = Rx.Observable.range(1, 3)
  .scan(function (acc, x) { return acc + x; });

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

// => Next: 1
// => Next: 3
// => Next: 6
// => Completed

/* With a seed */
var source = Rx.Observable.range(1, 3)
    .scan(function (acc, x) { return acc * x; }, 1);

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

// => Next: 1
// => Next: 2
// => Next: 6
// => Completed

Location

File:

• /src/core/linq/observable/scan.js

Dist:

• rx.all.js
• rx.all.compat.js
• rx.js
• rx.compat.js
• rx.lite.js
• rx.lite.compat.js

Prerequisites:

• None

NPM Packages:

• rx

NuGet Packages:

• RxJS-All
• RxJS-Main
• RxJS-Lite

Unit Tests:

• /tests/observable/scan.js