Javascript Array find even occurrence

Introduction

Find the first item that occurs an even number of times in an array.

Remember to handle multiple even-occurrence items and return the first one.

Return null if there are no even-occurrence items.

Example usage: 


var onlyEven = evenOccurrence([1, 7, 2, 4, 5, 6, 8, 9, 6, 4]);
console.log(onlyEven); //  4

var evenOccurrence = function(arr) {
  var occurance = {};
  for(var i = 0; i < arr.length; i++) {
    if(occurance[arr[i]] === undefined) {
      occurance[arr[i]] = 1;/*  w ww .j  a  va  2s. co m*/
    } else {
      occurance[arr[i]] += 1;
    }
  }
  for(var key in occurance) {
    if(occurance[key] >= 2) {
      return key;
    }
  }
  return null;
};
console.log(evenOccurrence([1, 7, 2, 4, 5, 6, 8, 9, 6, 4]));



PreviousNext

Related