mathjs/src/utils/product.js

Math.js is an extensive math library for JavaScript and Node.js. It features a flexible expression parser with support for symbolic computation, comes with a large set of built-in functions and constants, and offers an integrated solution to work with dif

/** @param {number} i
 *  @param {number} n
 *  @returns {number} product of i to n
 */
export function product (i, n) {
  if (n < i) {
    return 1
  }

  if (n === i) {
    return n
  }

  const half = (n + i) >> 1 // divide (n + i) by 2 and truncate to integer
  return product(i, half) * product(half + 1, n)
}