function mutation(arr) {
arr = [arr[0].toLowerCase(),arr[1].toLowerCase()];
var flag = [];
var count = 0;
for (var i = 0;i< arr[1].length; i++) {
flag[i] = arr[0].indexOf(arr[1][i]);
}
for(i=0;i<flag.length;i++){
if(flag[i]<0){
count++;
}
}
if(count===0){
return true;
}else{
return false;
}
}
console.log(mutation(["zyxwvutsrqponmlkjihgfedcba", "qrstuz"]));