Javascript Array numberOfOccurrences(nr)

// Description/*from   w w  w .j  a v a  2 s  .  co  m*/

// The numberOfOccurrences function must return the number of occurrences of an element in an array.

// var arr = [0,1,2,2,3];
// arr.numberOfOccurrences(0) === 1;
// arr.numberOfOccurrences(4) === 0;
// arr.numberOfOccurrences(2) === 2;
// arr.numberOfOccurrences("a") === 0;

Array.prototype.numberOfOccurrences = function(nr) {
  return this.filter(function(element) {
    return element === nr;
  }).length;
}