查字符串或者查对象值去重

let arr =(s)=> {
    let a = [];
    let max = 0;
    for(i =0 ; i < s.length; i++){
        console.log(a.indexOf(s[i]),a)
        while(a.indexOf(s[i])!=-1){
            a.shift();
        }
        a.push(s[i]);
        max = max>a.length? max:a.length;
    }
    return max;
};
console.log(arr("adddaasddddsad"))