JSFiddle - React, Tailwind, and code Playground

JavaScript

function getOpacityArray (sizeArray, max, range) {
    return $.map(sizeArray, function (n, i) {
        return (max - n) / range;
    });
}

var outputA   = [60, 59, 58, 57, 59], 
    baseSize  = 60, 
    sVariance = 4;

console.log(getOpacityArray(outputA, baseSize, sVariance));