JSFiddle - React, Tailwind, and code Playground
HTML
<span id="output"></span>
JavaScript
var arr = [4, 5, 6],
smax;
smax = arr.reduceRight(function (acc, curr) {
return (acc > curr) ? acc : --curr;
}, arr[arr.length - 1]);
document.getElementById('output').innerText = smax;
console.log(smax);