https://github.com/shinnn/array-has-duplicates

Check if an array includes duplicated values or not
https://github.com/shinnn/array-has-duplicates

Last synced: 26 days ago
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Check if an array includes duplicated values or not

• Host: GitHub
• URL: https://github.com/shinnn/array-has-duplicates
• Owner: shinnn
• License: isc
• Created: 2016-03-03T09:37:32.000Z (over 8 years ago)
• Default Branch: master
• Last Pushed: 2018-11-29T00:54:14.000Z (almost 6 years ago)
• Last Synced: 2024-10-11T21:16:16.674Z (about 1 month ago)
• Language: JavaScript
• Homepage: https://npm.runkit.com/array-has-duplicates
• Size: 72.3 KB
• Stars: 5
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# array-has-duplicates

[![npm version](https://img.shields.io/npm/v/array-has-duplicates.svg)](https://www.npmjs.com/package/array-has-duplicates)

[![Build Status](https://travis-ci.com/shinnn/array-has-duplicates.svg?branch=master)](https://travis-ci.com/shinnn/array-has-duplicates)

[![Coverage Status](https://img.shields.io/coveralls/shinnn/array-has-duplicates.svg)](https://coveralls.io/github/shinnn/array-has-duplicates)

Check if an `Array` includes duplicated values or not

```javascript

arrayHasDuplicates([1, 2, 3, 4, 5]); //=> false

arrayHasDuplicates([1, 2, 3, 4, 5, 1]); //=> true

```

## Installation

[Use](https://docs.npmjs.com/cli/install) [npm](https://docs.npmjs.com/about-npm/).

```

npm install array-has-duplicates

```

## API

### arrayHasDuplicates(*array*)

*array*: `Array`  

Return: `boolean`

It returns `true` if the array includes at least one pair of duplicated values, otherwise returns `false`.

```javascript

arrayHasDuplicates([3, 3, 3]); //=> true

arrayHasDuplicates([3, '3', [3]]); //=> false

```

*"Duplicated"* means a value is identical to another value in the ECMAScript [same-value equality](https://developer.mozilla.org/docs/Web/JavaScript/Equality_comparisons_and_sameness#Same-value_equality) level.

```javascript

arrayHasDuplicates([0, -0]); //=> false

```

Note that it ignores all empty indexes.

```javascript

arrayHasDuplicates([, undefined]);

//=> false, though array[0] and array[1] are both `undefined`

```

## Tips

When the difference between `-0` and `+0` is not important, there is no need to use this module and the [`Set`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set) constructor serves the purpose.

```javascript

function arrayHasDuplicatesLoose(arr) {

  return arr.length !== new Set(arr).size;

}

```

## License

[ISC License](./LICENSE) © 2018 Shinnosuke Watanabe