# first

#### signature: `first(predicate: function, select: function)`

## Emit the first value or first to pass provided expression.

***

💡 The counterpart to first is [**last**](/ko.learn-rxjs/rxjs/operators/filtering/last.md)!

💡 `First` will deliver an EmptyError to the Observer's error callback if the Observable completes before any next notification was sent. If you don't want this behavior, use `take(1)` instead.

***

[![Ultimate RxJS](https://drive.google.com/uc?export=view\&id=1qq2-q-eVe-F_-d0eSvTyqaGRjpfLDdJz)](https://ultimatecourses.com/courses/rxjs?ref=4)

### Examples

( [example tests](https://github.com/btroncone/learn-rxjs/blob/master/operators/specs/filtering/first-spec.ts) )

**Example 1: First value from sequence**

( [StackBlitz](https://stackblitz.com/edit/typescript-t8hseq?file=index.ts\&devtoolsheight=100) | [jsBin](http://jsbin.com/kayenuxoma/1/edit?js,console) | [jsFiddle](https://jsfiddle.net/btroncone/uncey4v9/) )

```js
// RxJS v6+
import { from } from 'rxjs';
import { first } from 'rxjs/operators';

const source = from([1, 2, 3, 4, 5]);
//no arguments, emit first value
const example = source.pipe(first());
//output: "First value: 1"
const subscribe = example.subscribe(val => console.log(`First value: ${val}`));
```

**Example 2: First value to pass predicate**

( [StackBlitz](https://stackblitz.com/edit/typescript-bw5byu?file=index.ts\&devtoolsheight=100) | [jsBin](http://jsbin.com/pujowawovu/1/edit?js,console) | [jsFiddle](https://jsfiddle.net/btroncone/pt36r8cu/) )

```js
// RxJS v6+
import { from } from 'rxjs';
import { first } from 'rxjs/operators';

const source = from([1, 2, 3, 4, 5]);
//emit first item to pass test
const example = source.pipe(first(num => num === 5));
//output: "First to pass test: 5"
const subscribe = example.subscribe(val =>
  console.log(`First to pass test: ${val}`)
);
```

**Example 3: Utilizing default value**

( [StackBlitz](https://stackblitz.com/edit/typescript-2pkzpv?file=index.ts\&devtoolsheight=100) | [jsBin](http://jsbin.com/qoganeleqa/1/edit?js,console) | [jsFiddle](https://jsfiddle.net/btroncone/owx2jdg1/3/) )

```js
// RxJS v6+
import { from } from 'rxjs';
import { first } from 'rxjs/operators';

const source = from([1, 2, 3, 4, 5]);
//no value will pass, emit default
const example = source.pipe(first(val => val > 5, 'Nothing'));
//output: 'Nothing'
const subscribe = example.subscribe(val => console.log(val));
```

### Additional Resources

* [first](https://rxjs.dev/api/operators/first) 📰 - Official docs
* [Filtering operator: take, first, skip](https://egghead.io/lessons/rxjs-filtering-operators-take-first-skip?course=rxjs-beyond-the-basics-operators-in-depth) 🎥 💵 - André Staltz

***

> 📁 Source Code: <https://github.com/ReactiveX/rxjs/blob/master/src/internal/operators/first.ts>


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