Converting alphabets to Greek letters in JavaScript

Problem

We are required to write a JavaScript function that takes in a string of uppercase English alphabets, str, as the first and the only argument.

Consider the following mapping between English and Greek letters −

A=α (Alpha) B=β (Beta) D=δ (Delta)
E=ε (Epsilon) I=ι (Iota) K=κ (Kappa)
N=η (Eta) O=θ (Theta) P=ρ (Rho)
R=π (Pi) T=τ (Tau) U=μ (Mu)
V=υ (Upsilon) W=ω (Omega) X=χ (Chi)
Y=γ (Gamma)

For all the alphabets that have a Greek mapping our function should create a new string in which the English letter is replaced by corresponding Greek letter and if there exists no mapping we should persist with the English alphabet.

For example, if the input to the function is −

Input

const str = 'PLAYING';

Output

const output = 'ρlαγιηg';

Example

Following is the code −

const str = 'PLAYING';
const convertLang = (str) => {
   const map = {
      a:'α',b:'β',d:'δ',e:'ε',
      i:'ι',k:'κ',n:'η',o:'θ',
      p:'ρ',r:'π',t:'τ',u:'μ',
      char:'υ',w:'ω',x:'χ',y:'γ'
   };
   return str.replace(/./g, char => {
      if (map[char.toLowerCase()]){
         return char === char.toUpperCase() ? map[char.toLowerCase()] : map[char];
      };
      return char.toLowerCase();

   });
};
console.log(convertLang(str))

Output

Ρlαγιηg