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.

参数

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

返回值

(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.

例

Finds an index

Not found

/* 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