A function that returns top K numbers from an integer array

find_first_k.js

/*
 * It gets an array of top k maximum or minimum elements from the given integer array
 * For example, findFirstK([2, 10, 1, 3, 4 ,6, 7], 3) returns [10, 7, 6], the top 3 maximum values from the array in the descending order
 * or findFirstK([2, 10, 1, 3, 4, 6, 7], 3, true) return [1, 2, 3]
 */
function shift(arr, k, value, asc) {
    if (k > arr.length - 1) {
        return;
    }

    var exp = value > arr[k];

    if (asc) {
        exp = value < arr[k];
    }

    if (!arr[k] || exp) {
        var count = arr.length - 1;

        while(count > k - 1) {
            arr[count] = arr[count - 1];
            count--;
        }

        arr[k] = value;

    } else {
        shift(arr, ++k, value, asc);
    }
}

module.exports = {
    findFirstK: function (int_list, k, asc) {
       // find max
       var max = new Array(k);
       max[0] = int_list[0];

       for (var i = 1;i < int_list.length;i++) {
           shift(max, 0, int_list[i], asc);
       }

       return max;
   }
};

find_first_k_test.js

var findK = require('./find_first_k');

var size = 50000000;

var int_list = new Array(size);
for (var i =0; i < size; i++) {
    int_list[i] = i;
}

var time = process.hrtime();
int_list.sort(function(a, b) {
    return b - a;
});

console.log([int_list[0], int_list[1], int_list[2]]);
console.log(hrtime(time));

var time = process.hrtime();
var top3 = findK.findFirstK(int_list, 3);
console.log(top3);
console.log(hrtime(time));

//var bottom3 = findK.findFirstK(int_list, 3, true);
//console.log(bottom3);
function hrtime(startAt) {
  if (!startAt) {
    return process.hrtime();
  }

  var diff = process.hrtime(startAt);
  return diff[0] * 1e3 + diff[1] * 1e-6;
}