normalizer.js

var val = 5184;
var set = [7921, 5184, 8836, 4761]

var average = set.reduce((memo, num) => {
  return memo + num;
}, 0) / set.length;

var max = Math.max.apply(this, set);
var min = Math.min.apply(this, set);

output =  (val - average) / (max - min) // equation

rounded = Math.round(output * 100)/100 // rounds to nearest 100th place. (1.23456 => 1.23)

console.log(output)
console.log(rounded)