Return maximum occurring character in an input string with functional JavaScript

maximumCharacter.js

/**
 * Javascript Algorithms.
 * Functional javascript using pure, recursive, compositing and ....
 * @Licence Don't use this code for anything ever! :) but if you do, give credit where credit is due, MIT.
 * @author Darik.
 * @GitHub neuralline
 *
 */

/**
 * MAXIMUM CHARACTER FUNCTION
 * @param {string} str please provide a string
 * @returns {[string, number]} ['max character', 'number of occurrence']
 * @description Return maximum occurring character in an input string
 *
 *
 */

const maximumCharacter = str => {
  const stringToObj = {}
  let max = ['', 0]
  const result = [...str.toLowerCase().trim()].map(char => {
    if (char.trim() === '') return
    stringToObj[char] = stringToObj[char] + 1 || 1
    max[1] < stringToObj[char] && (max = [char, stringToObj[char]])
  })

  return max
}

module.exports = maximumCharacter