How can I find the two positions with the two highest numbers in a multidimensional array?

I’m working in a JavaScript project where in this case I am trying to get the two arrays with the biggest value in position 2.

[-20.172, 35.251, 0],
[-16.368, 21.792, 26.81],
[-29.311, 18.393, 0],
[14.54, 15.23, 0],
[-1.61, 12.91, 27.692],
[0, 0, 0]

the intended answer should be like this:

[-16.368, 21.792, 26.81],
[-1.61, 12.91, 27.692]

I can’t sort by the ones that have a zero and the ones who doesn’t have it, some other cases in the project I’m working could possibly have different numbers on the position 2.

any suggestions?

>Solution :

Using Array#reduce:

const arr = [
  [-20.172, 35.251, 0],
  [-16.368, 21.792, 26.81],
  [-29.311, 18.393, 0],
  [14.54, 15.23, 0],
  [-1.61, 12.91, 27.692],
  [0, 0, 0]
];

const [max1Index, max2Index] = arr.reduce(([max1Index, max2Index], { 2: num }, index) => {
  const max1 = arr[max1Index][2], max2 = arr[max2Index][2];
  return num > max1
    ? [index, max1Index]
    : num > max2
      ? [max1Index, index]
      : [max1Index, max2Index];
}, [0, 0]);

console.log(arr[max1Index], arr[max2Index]);