Converting string to a binary string - JavaScript

We are required to write a JavaScript function that takes in a lowercase string and returns a new string in which all the elements between [a, m] are represented by 0 and all the elements between [n, z] are represented by 1.

Example

Following is the code −

const str = 'Hello worlld how are you';
const stringToBinary = (str = '') => {
   const s = str.toLowerCase();
   let res = '';
   for(let i = 0; i < s.length; i++){
      // for special characters
      if(s[i].toLowerCase() === s[i].toUpperCase()){
         res += s[i];
         continue;
      };
      if(s[i] > 'm'){
         res += 1;
      }else{
         res += 0;
      };
   };
   return res;
};
console.log(stringToBinary(str));

Output

Following is the output in the console −

00001 111000 011 010 111