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javascriptCheck if array has a duplicate value


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