找出字符串出现最多次数的字符以及次数

方式一:

var str = 'aaabbbbbccddddddddddx';
var obj = {};
for(var i=0;i<str.length;i++){
	var char = str.charAt(i);
	if( obj[char] ){
		obj[char]++;
	}else{
		obj[char] = 1;
	}
}
console.log( obj );
//统计出来最大值
var max = 0;
for( var key in obj ){
	if( max < obj[key] ){
		max = obj[key];
	}
}
//拿最大值去对比
for( var key in obj ){
	if( obj[key] == max ){
		console.log('最多的字符是'+key);
		console.log('出现的次数是'+max);
	}
}

方式二：new Map

const fun = (str) => {
        let map = new Map();
        let maxValue = '';
        let maxNum = 0;
        for (let item of str) {
            map.set(item, (map.get(item) || 0) + 1)
        }
        for (let [key, value] of map) {
            if (value > maxNum) {
                maxValue = key;
                maxNum = value
            }
        }
        return [maxValue, maxNum]
    }
    console.log(fun('abcabcabccc'))

方式三：for-of/for-in

const fun = (str) => {
        let obj = {};
        let maxValue = '';
        let maxNum = 0;
        for (let key of str) {
            obj[key] = !obj[key] ? 1 : obj[key] + 1
        }
        for (let key in obj) {
            if (obj[key] > maxNum) {
                maxValue = key;
                maxNum = obj[key]
            }
        }
        return [maxValue, maxNum]
    }
       console.log(fun('abcabcabccc'))

方式四:正则

const fun = (str) => {
        //出现次数字符最多
        let maxValue = '';
        //出现次数字符最多的数字
        let maxNum = 0;
        //排序
        str=str.split("").sort().join("")
        //正则匹配
        let reg=/(\w)\1+/g;
        str.replace(reg, (val,item)=>{
            if(val.length>maxNum){
                maxNum=val.length
                maxValue=item
            }
        })
        console.log(str.match(reg))
        return [maxValue, maxNum]
    }
     console.log(fun('abcabcabccc'))