1、核心算法：利用 charAt() 遍历这个字符串

2、把每个字符都存储给对象，如果对象没有该属性就为1，如果存了就+1

3、遍历对象，得到最大值及出现次数和该字符

let str = "aozisodsdkksdsd"

        let obj = {}

        for (let i = 0; i < str.length; i++) {

            let chars = str.charAt(i)

            if (obj[chars]) {

                obj[chars]++;

            } else {

                obj[chars] = 1

            }

        }

        console.log(obj)

        let max = 0;

        let ch = ''

        for (let key in obj) {

            if (obj[key] > max) {

                max = obj[key]

                ch = key

            }

        }

        console.log(`字符串中出现次数最多的字符是${ch}，出现的次数是${max}次`)