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"))