javascript-algorithms/src/algorithms/math/horner-method/hornerMethod.js

/**
 * Returns the evaluation of a polynomial function at a certain point.
 * Uses Horner's rule.
 *
 * @param {number[]} coefficients - i.e. [4, 3, 2] for (4 * x^2 + 3 * x + 2)
 * @param {number} xVal
 * @return {number}
 */
export default function hornerMethod(coefficients, xVal) {
  return coefficients.reduce(
    (accumulator, currentCoefficient) => {
      return accumulator * xVal + currentCoefficient;
    },
    0,
  );
}