1-identifiers.js

'use strict';

// Arguments instead of mutable variables assignment

const { PI, sqrt } = Math;
const square = (x) => x * x;

// Imperative

const truncatedConeVolume = ({ height, r1, r2 }) => {
  const k = PI / 3;
  const sr1 = square(r1);
  const sr2 = square(r2);
  return k * height * (sr1 + r1 * r2 + sr2);
};

const truncatedConeArea = ({ height, r1, r2 }) => {
  const sr1 = square(r1);
  const sr2 = square(r2);
  const l = sqrt(square(height) + square(r2 - r1));
  return PI * (sr1 + sr2 + l * (r1 + r2));
};

{
  const cone = { height: 7, r1: 10, r2: 15 };
  cone.v = truncatedConeVolume(cone);
  cone.s = truncatedConeArea(cone);
  console.dir(cone);
}

// Functional

const volume = (height, r1, r2) => (PI * height / 3) *
  (square(r1) + r1 * r2 + square(r2));

const area = (height, r1, r2) => PI * (
  square(r1) + square(r2) +
  sqrt(square(height) + square(r2 - r1)) * (r1 + r2)
);

const cone = (height, r1, r2, volume, area) => ({
  height, r1, r2, volume, area
});

const calcCone = ({ height, r1, r2 }) => cone(
  height, r1, r2, volume(height, r1, r2), area(height, r1, r2)
);

{
  const cone = calcCone({ height: 7, r1: 10, r2: 15 });
  console.dir(cone);
}