Javascript Array numberOfOccurrences(desVal)

// 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(desVal) {
  
  var counter = 0;
  this.forEach(function(value){
    if(value === desVal){
      counter++;//www .j  a v  a 2 s .  c o  m
    }
  });
  
  return counter;
};