# elementAt

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

1. `index` *(`Number`)*: The zero-based index of the element to retrieve.
2. `[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

### Not found

```javascript
/* 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
```


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