输入一段字符串，找出出现最多的字符串，和出现的次数

let str='dfdsafbuhdfhjlvasdfusdljasdvflasudfvasdpufvsih';

let ldf={},word;

let len=str.length;

for (let i=0;i<len;i++){

word=str[i];

if(ldf[word]){

ldf[word]++

}else {

ldf[word]=1;

}

}

var maxNum=0;

let arr=[];

for(key in ldf){

if(maxNum<ldf[key]){

maxNum=ldf[key];

}

}

for(key in ldf){

if(ldf[key]==maxNum){

arr.push(key)

}

}

console.log(ldf)

console.log('出现最多的字母是'+arr,'出现次数是'+maxNum+'次')