> For the complete documentation index, see [llms.txt](https://soufatn.gitbook.io/rxjs-book/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://soufatn.gitbook.io/rxjs-book/summary/observable/observable_instance_methods/first.md).

# first

Returns the first element of an observable sequence that satisfies the condition in the predicate, or a default value if no such element exists. If no default value is given, then `onError` will be called.

## Arguments

`Rx.Observable.prototype.first([predicate], [thisArg], [defaultValue])`

1. `[predicate]` *(`Function`)*: A predicate function to evaluate for elements in the source sequence. The callback is called with the following information:
   1. the value of the element
   2. the index of the element
   3. the Observable object being subscribed
2. `[thisArg]` *(`Any`)*: Object to use as `this` when executing the predicate.
3. `[defaultValue]` *(`Any`)*: Default value if no such element exists.

`Rx.Observable.prototype.first([settings])`

1. `[settings]` *(`Object`)*: An object with the following fields
   * `[predicate]` *(`Function`)*: A predicate function to evaluate for elements in the source sequence. The callback is called with the following information:
     1. the value of the element
     2. the index of the element
     3. the Observable object being subscribed
   * `[thisArg]` *(`Any`)*: Object to use as `this` when executing the predicate.
   * `[defaultValue]` *(`Any`)*: Default value if no such element exists.

## Returns

*(`Observable`)*: An observable sequence that contains elements from the input sequence that satisfy the condition.

## Example

### No Match

### Without a predicate

### With a predicate

```javascript
/* With a default value */
var source = Rx.Observable.range(0, 10)
  .first({
    predicate: function (x, idx, obs) { return x > 10; },
    defaultValue: 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
```