JSFiddle - React, Tailwind, and code Playground

JavaScript

Array.prototype.max = function () {
    return Math.max.apply(null, this);
};

Array.prototype.min = function () {
    return Math.min.apply(null, this);
};

var arr = [];

arr[0] = parseInt(prompt("Enter 1st number"));

arr[1] = parseInt(prompt("Enter 2nd number"));

arr[2] = parseInt(prompt("Enter 3rd number"));

var final = (arr[0] * 2) + (arr[1] * 3) + (arr[2] * 4);


document.write(final + "<br/>");
document.write(Math.min.apply(null, arr) + "<br/>");
document.write(Math.max.apply(null, arr) + "<br/>");
document.write(arr.reduce(add, 0));

function add(a, b) {
    return a + b;
}