744. Find Smallest Letter Greater Than Target.js

/**
 * @param {character[]} letters
 * @param {character} target
 * @return {character}
 */
 var nextGreatestLetter = function(letters, target) {
    let left=0;
    let right=letters.length;
    while(left<right){
        let mid=Math.floor((left+right)/2);
        if(letters[mid]>target){
            right=mid;
        }
        else{
            left=mid+1;
        }
    }
    return letters[left%letters.length];
    
    
};