JavaScript:实现给定一串字符,返回出现频率最高的字符算法
/**
* @function maxCharacter
* @example - Given a string of characters, return the character that appears the most often. Example: input = "Hello World!" return "l"
* @param {string} str
* @param {RegExp} ignorePattern - ignore the char in str that is not required
* @returns {string} - char
*/
const maxCharacter = (str, ignorePattern) =