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: 3 months ago
JSON representation
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 9 years ago)
- Default Branch: master
- Last Pushed: 2018-11-29T00:54:14.000Z (over 6 years ago)
- Last Synced: 2024-10-18T19:58:02.173Z (9 months 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
Awesome Lists containing this project
README
# array-has-duplicates
[](https://www.npmjs.com/package/array-has-duplicates)
[](https://travis-ci.com/shinnn/array-has-duplicates)
[](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