> For the complete documentation index, see [llms.txt](https://chasethestar.gitbook.io/ko.learn-rxjs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://chasethestar.gitbook.io/ko.learn-rxjs/rxjs/operators/filtering/distinctuntilchanged.md).

# distinctUntilChanged

#### signature: `distinctUntilChanged(compare: function): Observable`

## Only emit when the current value is different than the last.

***

💡 distinctUntilChanged uses `===` comparison by default, object references must match!

💡 If you want to compare based on an object property, you can use [`distinctUntilKeyChanged`](/ko.learn-rxjs/rxjs/operators/filtering/distinctuntilkeychanged.md) 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 1: distinctUntilChanged with basic values**

( [StackBlitz](https://stackblitz.com/edit/typescript-bsb8mw?file=index.ts\&devtoolsheight=100) )

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

// only output distinct values, based on the last emitted value
const source$ = from([1, 1, 2, 2, 3, 3]);

source$
  .pipe(distinctUntilChanged())
  // output: 1,2,3
  .subscribe(console.log);
```

**Example 2: distinctUntilChanged with objects**

( [StackBlitz](https://stackblitz.com/edit/typescript-moe7mh?file=index.ts\&devtoolsheight=100) )

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

const sampleObject = { name: 'Test' };

//Objects must be same reference
const source$ = from([sampleObject, sampleObject, sampleObject]);

// only emit distinct objects, based on last emitted value
source$
  .pipe(distinctUntilChanged())
  // output: {name: 'Test'}
  .subscribe(console.log);
```

**Example 3: Using custom comparer function**

( [StackBlitz](https://stackblitz.com/edit/typescript-hzta27?file=index.ts\&devtoolsheight=100) )

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

// only output distinct values, based on the last emitted value
const source$ = from([
  { name: 'Brian' },
  { name: 'Joe' },
  { name: 'Joe' },
  { name: 'Sue' }
]);

source$
  // custom compare for name
  .pipe(distinctUntilChanged((prev, curr) => prev.name === curr.name))
  // output: { name: 'Brian }, { name: 'Joe' }, { name: 'Sue' }
  .subscribe(console.log);
```

### Related Recipes

* [Lockscreen](/ko.learn-rxjs/rxjs/recipes/lockscreen.md)
* [Save Indicator](/ko.learn-rxjs/rxjs/recipes/save-indicator.md)
* [Type Ahead](/ko.learn-rxjs/rxjs/recipes/type-ahead.md)

### Additional Resources

* [distinctUntilChanged](https://rxjs.dev/api/operators/distinctUntilChanged) 📰 - Official docs
* [distinctUntilChanged](https://indepth.dev/reference/rxjs/operators/distinct-until-changed) - In Depth Dev Reference
* [Filtering operator: distinct and distinctUntilChanged](https://egghead.io/lessons/rxjs-filtering-operators-distinct-and-distinctuntilchanged?course=rxjs-beyond-the-basics-operators-in-depth) 🎥 💵 - André Staltz

***

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