how to find number of duplicate value in array code example

Example 1: how to get duplicate values from array in javascript

var array = [1, 2, 2, 3, 3, 4, 5, 6, 2, 3, 7, 8, 5, 22, 1, 2, 511, 12, 50, 22];

console.log([...new Set(
  array.filter((value, index, self) => self.indexOf(value) !== index))]
);

Example 2: find duplicates and their count in an array javascript

var counts = {};
your_array.forEach(function(x) { counts[x] = (counts[x] || 0)+1; });