Generate ecommerce promo code with Typescript

promo.ts

// Don't use characters that look similar in certain fonts, I/L/1, 0/O, B/8 etc.
const charSet = "ACDEFGHJKMNPQRSTUVWXYZ2345679";
const delimiter = '-'

interface GeneratePromoCodeParams {
  len: number;
}

export const generatePromoCode = (params: GeneratePromoCodeParams) => {
  let result = "";
  for (let i = 0; i < params.len; i++) {
    result += charSet.charAt(Math.floor(Math.random() * charSet.length));
  }
  return result;
};

// For display purposes
interface ChunkPromoCodeParams {
  size: number;
}

export const chunkPromoCode = (code: string, params: ChunkPromoCodeParams) => {
  let result = "";
  for (let i = 0; i < code.length; i++) {
    result += code[i];
    if ((i + 1) % params.size === 0 && i !== code.length - 1) {
      result += delimiter;
    }
  }
  return result;
};

// If user inputs with dashes, we can unchunk to then test validity.
export const unchunkPromoCode = (code: string) => {
  return code.replaceAll(delimiter, "");
};