Moving every alphabet forward by 10 places in JavaScript

Problem

We are required to write a JavaScript function that takes in a string of English alphabets. Our function should push every alphabet forward by 10 places. And if it goes past 'z', we should start again at 'a'.

Example

Following is the code −

const str = 'sample string';
const moveStrBy = (num = 10) => {
   return str => {
      const calcStr = (ch, code) => String
      .fromCharCode(code + (ch.charCodeAt(0) - code + num) % 26);
      const ACode = 'A'.charCodeAt(0);
      const aCode = 'a'.charCodeAt(0);
      return str.replace(/[a-z]/gi, ch => (
         ch.toLowerCase() == ch
         ? calcStr(ch, aCode)
         : calcStr(ch, ACode)
      ));
   };
};
const moveByTen = moveStrBy();
console.log(moveByTen(str));

Output

ckwzvo cdbsxq