`Rx.Observable.prototype.elementAt(index, [defaultValue])`

Ⓢ

Returns the element at a specified index in a sequence. If the specified index is out of bounds and no default value was given onError will be called with an error, however, if a default value has been specified, that value will be returned via an onNext call.

Arguments

index (Number): The zero-based index of the element to retrieve.
[defaultValue] (Any): Default value if no such element exists.

Returns

(Observable): An observable sequence that produces the element at the specified position in the source sequence. If the specified index is out of bounds and no default value was given onError will be called with an error, however, if a default value has been specified, that value will be returned via an onNext call.

Example

/* Finds an index */
var source = Rx.Observable.from([1,2,3,4])
    .elementAt(1);

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

// => Next: 2
// => Completed

/* With default value */
var source = Rx.Observable.from([1,2,3,4])
  .elementAt(4, 42);

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

// => Next: 42
// => Completed