Check if a string is sorted in JavaScript

We are required to write a JavaScript function that takes in a string and checks whether it is sorted or not.

For example −

isSorted('adefgjmxz')  // true
isSorted('zxmfdba')     // true
isSorted('dsfdsfva')     // false

Example

Following is the code −

const str = 'abdfhlmxz';
const findDiff = (a, b) => a.charCodeAt(0) - b.charCodeAt(0);
const isStringSorted = (str = '') => {
   if(str.length < 2){
      return true;
   };
   let res = ''
   for(let i = 0; i < str.length-1; i++){
      if(findDiff(str[i+1], str[i]) > 0){
         res += 'u';
      }else if(findDiff(str[i+1], str[i]) < 0){
         res += 'd';
      };
      if(res.indexOf('u') && res.includes('d')){
         return false;
      };
   };
   return true;
};
console.log(isStringSorted(str));

Output

This will produce the following output in console −

true