problem1.ts

export const problem1 = function (length = 12) {
  let result = "";
  const characters = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
  const charactersLength = characters.length;
  for (let i = 0; i < length; i++) {
    result += characters.charAt(Math.floor(Math.random() * charactersLength));
  }
  return result;
};

problem2.ts

export const problem2 = (str: string) => {
  return str.replace(/[^a-zA-Z0-9-]/g, "-").toLowerCase();
};

problem3.ts

export const prob3_a = (e) => {
  return e.replace(/_([a-z])/g, (g) =>  g[1].toUpperCase());
};

export const prob3_b = (e) => {
  return e.match(/([A-Z])/g).reduce(
    (str, c) => str.replace(new RegExp(c), '_' + c.toLowerCase()),
    e
  )
  .substring((e.slice(0, 1).match(/([A-Z])/g)) ? 1 : 0);
};