How to know the name of the variable containing the max number after Math.max()

Question

Let's say I have the following variables:

var num1 = 48;
var num2 = 420;
var num3 = 39;

And I want to know the max value, for that I use:

var max = Math.max(num1, num2, num3);

Is there a way to know that num2 was the max number? This example only has 3 variables, but let's say I have 20 or 500. I need to know the max value and its variable name in the most efficient way.

Answer 1

You cannot know the variable name because the variable name is not passed into javascript functions, only the values, but you can have a workaround

with arrays:

var numbers = [48,420,39];

const index = numbers.indexOf(Math.max(...numbers))

console.log(`The max value is the ${index+1}nth value in the array`)

with objects

var num1 = 48;
var num2 = 420;
var num3 = 39;

var numbers = {num1, num2, num3}

const maxVal = Math.max(...Object.values(numbers))
const key = Object.keys(numbers).find(key => numbers[key] === maxVal)

console.log(key, maxVal)

Answer 2

Since you are using var, it will get binded to the window object. Then you can iterate over window object, and get the name of variable. Also, if you follow same naming convention, like num1, num2 etc, you can use a if condition to check if num is present in key or not.

var num1 = 48;
var num2 = 420;
var num3 = 39;

var max = Math.max(num1, num2, num3);

let s = Object.keys(window).filter(key => {
      if (key.includes("num")) {
          return window[key] == max
        }
      });

console.log(s)