JavaScript finding the largest integer in an array of arrays

Question

function largestOfFour(arr) {
    var newArray = [];
    for(var i =0; i <=arr.length-1; i++){
        console.log(arr[i]);
        newArray[i] = Math.max(arr[i]);
           


        

Answer 1

Using lodash

var x = ([[4, 5, 1, 3], [13, 27, 18, 26], [32, 35, 37, 39], [1000, 1001, 857, 1]]);
_.flatten(x).max();

Answer 2

You are passing an array to Math.max and expect it to return the maximum in that array.

However, Math.max returns the maximum among its arguments. So use

var newArray = [];
for(var i =0; i < arr.length; ++i)
  newArray[i] = Math.max.apply(void 0, arr[i]);

In ES6, you can use arrow functions and the spread operator to simplify:

arr.map(a => Math.max(...a));

Answer 3

It won't work like that. Math.max expect separate numbers. You can get desired output using apply

function largestOfFour(arr) {
    return arr.map(function(subArr){
        return Math.max.apply(Math, subArr);
    });
}

Answer 4

If you want the ultimate max do this.

var original = [[4, 5, 1, 3], [13, 27, 18, 26], [32, 35, 37, 39], [1000, 1001, 857, 1]];
Math.max.apply(null, original.map(function(arr) { return Math.max.apply(null, arr); }));

or if you want a the max of each array just do

original.map(function(arr) { return Math.max.apply(null, arr); });

Answer 5

Edited: In order to add values to the array, I'd suggest using the push methodn. As in: NewArray.push(Math.max(...sub[i])); or newarray.push(math.max.apply(null, sub[i]). An alternative is alocating, when declarating the array, the size it will take: Var newArray = new Array(arr.length); There's this new spread operator (...) in javascript !