How can I return a different array?

Question

I need to return an array consisting of the largest number from each provided sub-array. So, I've written the following code and it works but I have: [[25],[48],[21],[-3]] instead of [25,48,21,-3] . Can I change something to get the right answer?

 function largestOfFour(arr) { for (let i = 0; i < arr.length; i++) { arr[i].sort(function(a,b) { return b - a; }).map(function() { return arr[i].splice(1); }) } return arr; } var result = largestOfFour([[17, 23, 25, 12], [25, 7, 34, 48], [4, -10, 18, 21], [-72, -3, -17, -10]]); console.log(result); 

Answer 1

You could use map with spread syntax ... to return 1D array as pointed out by @str .

 function largestOfFour(arr) { return arr.map(a => Math.max(...a)) } const arr = [[17, 23, 25, 12], [25, 7, 34, 48], [4, -10, 18, 21], [-72, -3, -17, -10]] const result = largestOfFour(arr); console.log(result) 

You could also use reduce

 function largestOfFour(arr) { return arr.reduce((r, a) => r.concat(Math.max(...a)), []) } const arr = [[17, 23, 25, 12], [25, 7, 34, 48], [4, -10, 18, 21], [-72, -3, -17, -10]] const result = largestOfFour(arr); console.log(result) 

Answer 2

Loop and sort, then return the first element of each sub-array with map ;

function largestOfFour(arr) {
   for (let i = 0; i < arr.length; i++) {
      arr[i].sort(function(a,b) {
         return b - a;
      });
   }
   return arr.map(array => array[0]);
}

Better still, do it in one.

function largestOfFour(arr) {
    return arr.map(array => array.sort((a,b) => b - a)[0]);
}

Answer 3

get the first character of each array using [0] index like this

function largestOfFour(arr) {
  for (let i = 0; i < arr.length; i++) {

    arr[i].sort(function(a,b) {
      return b - a;

    }).map(function() {
       // HERE
       return arr[i].splice(1)[0];

    })

  }
  return arr;
}

largestOfFour([[17, 23, 25, 12], [25, 7, 34, 48], [4, -10, 18, 21], [-72, -3, -17, -10]]);

Answer 4

You could map the first element of the descending sorted elements.

 function largestOfFour(array) { return array.map(a => a.sort((a, b) => b - a)[0]); } console.log(largestOfFour([[17, 23, 25, 12], [25, 7, 34, 48], [4, -10, 18, 21], [-72, -3, -17, -10]])); 

Answer 5

You can use map which will return a new array and then use Math.max to get the maximum value form the array

 function largestOfFour(arr) { return arr.map(item => { return [Math.max.apply(null, item)] }) } console.log(largestOfFour([ [17, 23, 25, 12], [25, 7, 34, 48], [4, -10, 18, 21], [-72, -3, -17, -10] ])); 

Answer 6

you can use flat function for it

var arr1 = [1, 2, [3, 4]];
    arr1.flat(); 
    // [1, 2, 3, 4]

    var arr2 = [1, 2, [3, 4, [5, 6]]];
    arr2.flat();
    // [1, 2, 3, 4, [5, 6]]

    var arr3 = [1, 2, [3, 4, [5, 6]]];
    arr3.flat(2);
    // [1, 2, 3, 4, 5, 6]