javascript add to array with duplicates code example

Example 1: duplicate numbers in an array javascript

[1, 1, 2, 2, 3].filter((element, index, array) => array.indexOf(element) !== index) // [1, 2]

Example 2: javascript create array with repeated values

Array(5).fill(2)
//=> [2, 2, 2, 2, 2]