验证一个字符串中哪个字符串出现的次数最多，出现多少次？

 // 方法1：
    let str = 'zhumolanglafengyouyihah';
    let obj={};
    [].forEach.call(str,char=>{
      if(typeof obj[char]!=='undefined'){
        obj[char]++;
        return;
      }
      obj[char]=1;
    })
    let max=1;
    let res = [];
    for(let key in obj){
      let item = obj[key];
      item > max ? max = item : null;
    }
    for(let key in obj){
      let item = obj[key];
      if(item === max){
        res.push(key);
      }
    }
    console.log(`出现次数最多的是：${res},出现了${max}`,obj);//出现次数最多的是：h,a,出现了3
    

    //方法2排序
      let str = 'zhumolanglafengyouyihah';
          str = str.split('').sort((a,b)=>a.localeCompare(b)).join('');
          console.log(str); //aaaefgghhhillmnnoouuyyz
          let reg = /([a-zA-Z])1+/g;
          let ary=str.match(reg).sort((a,b)=>b.length-a.length);
          let max = ary[0].length;
          let res =[ary[0].substr(0,1)]
          for(let i=1;i<ary.length;i++){
            if(ary[i].length < max){
              break;
            }
            res.push(ary[i].substr(0,1))
          }
          console.log(`出现次数最多的是：${res},出现了${max}`); //出现次数最多的是：a,h,出现了3
        

  //方法3
      let str = 'zhumolanglafengyouyihah';
      let max = 0,
          res = [],
          flag=false;
          str = str.split('').sort((a,b)=>a.localeCompare(b)).join('');
          for(let i = str.length;i>0;i--){
            let reg = new RegExp('([a-zA-Z])\1{'+(i-1)+'}','g');
            str.replace(reg,(content,$1)=>{
              res.push($1);
              max=i;
              flag=true;
            })
            if(flag)break;
          }
          console.log(`出现次数最多的是：${res},出现了${max}`);//出现次数最多的是：a,h,出现了3