reverse a function

formula.js

const REV_FORM = Symbol("reverse-formula");
const SCALE = 10;

function createReverseFormula(formula) {
  const list = new Array(SCALE + 1).fill(0).map((_, i) => {
    const inp = i / SCALE;
    const out = formula(inp);
    return { inp, out };
  });

  return output => {
    let distance = Number.POSITIVE_INFINITY;
    let closest;
    list.forEach(({ inp, out }) => {
      const dist = Math.abs(output - out);
      if (dist < distance) {
        distance = dist;
        closest = inp;
      }
    });
    return closest;
  };
}

export function reverseFormula(formula) {
  let rev = formula[REV_FORM];
  if (!rev) {
    rev = createReverseFormula(formula);
    formula[REV_FORM] = rev;
  }
  return rev;
}