Find duplicate values in a array

by Elena Lembersky

JavaScript

function find_duplicate_in_array(arra1) {
        var object = {};
        var result = [];

        arra1.forEach(function (item) {
          if(!object[item])
              object[item] = 0;
            object[item] += 1;
        })

        for (var prop in object) {
           if(object[prop] >= 2) {
               result.push(prop);
           }
        }

        return result;

    }

    console.log(find_duplicate_in_array([1, 2, -2, 4, 5, 4, 7, 8, 7, 7, 71, 3, 6]));