How do I get the second largest element from an array in javascript [closed]

Answer 1

The simplest solution is to sort :

// here's your array :
var stringArray = new Array('20','120','111','215','54','78');

// let's convert it to a real array of numbers, not of strings :
var intArray = stringArray.map(Number);

// now let's sort it and take the second element :
var second = intArray.sort(function(a,b){return b-a})[1]; 

If you don't want the simplest but the fastest (you probably don't need it), then you'd have to write your for loop and store the two greatest elements while looping.

Answer 2

Sort your array from smallest to largest, then grab second one from the end with .length-2

var myArray =['20','120','111','215','54','78'];
var secondLargest = myArray.sort(function(a,b){return a - b})[myArray.length-2];
alert(secondLargest); //120;

Answer 3

var secondMax = function (){ 
    var arr = [20, 120, 111, 215, 54, 78]; // use int arrays
    var max = Math.max.apply(null, arr); // get the max of the array
    arr.splice(arr.indexOf(max), 1); // remove max from the array
    return Math.max.apply(null, arr); // get the 2nd max
};

demo

UPDATE

As pointed out by davin the performance could be enhanced by not doing a splice but temporarily replacing the max value with -Infininty:

var secondMax = function (arr){ 
    var max = Math.max.apply(null, arr), // get the max of the array
        maxi = arr.indexOf(max);
    arr[maxi] = -Infinity; // replace max in the array with -infinity
    var secondMax = Math.max.apply(null, arr); // get the new max 
    arr[maxi] = max;
    return secondMax;
};

Anyway, IMHO the best algorithm is Jack's. 1 pass, with conversion to number. Mine is just short, using builtin methods and only wanted to provide it as an alternative, to show off all the different ways you can achieve the goal.

Answer 4

First sort it backwards and then get the second element:

['20','120','111','215','54','78'].sort(function(a, b) { return b - a; })[1];
// '120'

Obviously works with strings too.

Answer 5

You can try this:

function second_highest(arr)
{
  var second_highest = arr.sort(function(a, b) { return b - a; })[1];
  return second_highest;

}

Answer 6

Sort the array and then return the second index.

var arr = ['20','120','111','215','54','78'];

arr.sort(function(a,b){
    return b-a;
});

console.log(arr[1]);