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# arr-diff [](https://www.npmjs.com/package/arr-diff) [](https://npmjs.org/package/arr-diff) [](https://travis-ci.org/jonschlinkert/arr-diff)
> Returns an array with only the unique values from the first array, by excluding all values from additional arrays using strict equality for comparisons.
## Install
Install with [npm](https://www.npmjs.com/):
```sh $ npm install --save arr-diff ```
Install with [yarn](https://yarnpkg.com):
```sh $ yarn add arr-diff ```
Install with [bower](https://bower.io/)
```sh $ bower install arr-diff --save ```
## Usage
Returns the difference between the first array and additional arrays.
```js var diff = require('arr-diff');
var a = ['a', 'b', 'c', 'd']; var b = ['b', 'c'];
console.log(diff(a, b)) //=> ['a', 'd'] ```
## Benchmarks
This library versus [array-differ](https://github.com/sindresorhus/array-differ), on April 14, 2017:
``` Benchmarking: (4 of 4) · long-dupes · long · med · short
# benchmark/fixtures/long-dupes.js (100804 bytes)
arr-diff-3.0.0 x 822 ops/sec ±0.67% (86 runs sampled) arr-diff-4.0.0 x 2,141 ops/sec ±0.42% (89 runs sampled) array-differ x 708 ops/sec ±0.70% (89 runs sampled)
fastest is arr-diff-4.0.0
# benchmark/fixtures/long.js (94529 bytes)
arr-diff-3.0.0 x 882 ops/sec ±0.60% (87 runs sampled) arr-diff-4.0.0 x 2,329 ops/sec ±0.97% (83 runs sampled) array-differ x 769 ops/sec ±0.61% (90 runs sampled)
fastest is arr-diff-4.0.0
# benchmark/fixtures/med.js (708 bytes)
arr-diff-3.0.0 x 856,150 ops/sec ±0.42% (89 runs sampled) arr-diff-4.0.0 x 4,665,249 ops/sec ±1.06% (89 runs sampled) array-differ x 653,888 ops/sec ±1.02% (86 runs sampled)
fastest is arr-diff-4.0.0
# benchmark/fixtures/short.js (60 bytes)
arr-diff-3.0.0 x 3,078,467 ops/sec ±0.77% (93 runs sampled) arr-diff-4.0.0 x 9,213,296 ops/sec ±0.65% (89 runs sampled) array-differ x 1,337,051 ops/sec ±0.91% (92 runs sampled)
fastest is arr-diff-4.0.0 ```
## About
### Related projects
* [arr-flatten](https://www.npmjs.com/package/arr-flatten): Recursively flatten an array or arrays. This is the fastest implementation of array flatten. | [homepage](https://github.com/jonschlinkert/arr-flatten "Recursively flatten an array or arrays. This is the fastest implementation of array flatten.") * [array-filter](https://www.npmjs.com/package/array-filter): Array#filter for older browsers. | [homepage](https://github.com/juliangruber/array-filter "Array#filter for older browsers.") * [array-intersection](https://www.npmjs.com/package/array-intersection): Return an array with the unique values present in _all_ given arrays using strict equality… [more](https://github.com/jonschlinkert/array-intersection) | [homepage](https://github.com/jonschlinkert/array-intersection "Return an array with the unique values present in _all_ given arrays using strict equality for comparisons.")
### Contributing
Pull requests and stars are always welcome. For bugs and feature requests, [please create an issue](../../issues/new).
### Contributors
| **Commits** | **Contributor** | | --- | --- | | 33 | [jonschlinkert](https://github.com/jonschlinkert) | | 2 | [paulmillr](https://github.com/paulmillr) |
### Building docs
_(This project's readme.md is generated by [verb](https://github.com/verbose/verb-generate-readme), please don't edit the readme directly. Any changes to the readme must be made in the [.verb.md](.verb.md) readme template.)_
To generate the readme, run the following command:
```sh $ npm install -g verbose/verb#dev verb-generate-readme && verb ```
### Running tests
Running and reviewing unit tests is a great way to get familiarized with a library and its API. You can install dependencies and run tests with the following command:
```sh $ npm install && npm test ```
### Author
**Jon Schlinkert**
* [github/jonschlinkert](https://github.com/jonschlinkert) * [twitter/jonschlinkert](https://twitter.com/jonschlinkert)
### License
Copyright © 2017, [Jon Schlinkert](https://github.com/jonschlinkert). Released under the [MIT License](LICENSE).
***
_This file was generated by [verb-generate-readme](https://github.com/verbose/verb-generate-readme), v0.5.0, on April 14, 2017._
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