how to find the index of the maximum value in an array javascript code example

Example 1: how to find index of max number in js

var a = [0, 21, 22, 7];
var indexOfMaxValue = a.reduce((iMax, x, i, arr) => x > arr[iMax] ? i : iMax, 0);

document.write("indexOfMaxValue = " + indexOfMaxValue); // prints "indexOfMaxValue = 2"

Example 2: Find the maximum number of an array js

var arr = [1, 2, 3];
var max = arr.reduce(function(a, b) {
  return Math.max(a, b);
});