const isDup = (arr) => arr.length !== new Set(arr).size
isDup([1,2,3,4,5]) // false
isDup([1,1,2,3,4]) // true
isDup(new Array(5))// true. [undefined, undefined,...] のため
なお、[...new Set(array)] とやれば、重複のない配列が作れる
More than 5 years have passed since last update.
Register as a new user and use Qiita more conveniently
- You get articles that match your needs
- You can efficiently read back useful information
- You can use dark theme
List of users who liked
1312