javascriptCheck if array has a duplicate value

var has_duplicates = new Set(arr).size !== arr.length;ctrl + cyoutubegithub

`var has_duplicates` will contain `true` if `arr` array has any duplicate values	`new Set(arr)` form a set with values of the array. A set is an javascript object that has only non-duplicate values
`!== arr.length` If size of the newly formed set is equal to size of the array, you don't have any duplicates, returns `false` else returns `true`