Username

function solution(input) {
  let username = input.shift();
  let token = input.shift();

  while (token !== `Sign up`) {
    let [comand, checkOne, checkTwo] = token.split(` `);

    if (comand === `Case` && checkOne === `lower`) {
      username = username.toLowerCase();
      console.log(username);
    } else if (comand === `Case` && checkOne === `upper`) {
      username = username.toUpperCase();
      console.log(username);
    } else if (comand === `Reverse`) {
      reverse(username, checkOne, checkTwo);
    } else if (comand === `Cut`) {
      username = cut(username, checkOne);
    } else if (comand === `Replace`) {
      username = replace(username, checkOne);
    } else if (comand === `Check`) {
      check(username, checkOne);
    }

    token = input.shift();
  }

  function reverse(string, startIndex, endIndex) {
    startIndex = Number(startIndex);
    endIndex = Number(endIndex);

    if (
      startIndex >= 0 &&
      startIndex < string.length &&
      endIndex >= 0 &&
      endIndex < string.length
    ) {
      let subst = string
        .substring(startIndex, endIndex + 1)
        .split(``)
        .reverse()
        .join(``);
      console.log(subst);
    }

    return string;
  }

  function cut(string, substring) {
    if (string.includes(substring)) {
      string = string.replace(substring, ``);

      console.log(string);
    } else {
      console.log(`The word ${string} doesn't contain ${substring}.`);
    }

    return string;
  }

  function replace(string, char) {
    while (string.includes(char)) {
      string = string.replace(char, `*`);
    }
    console.log(string);
    return string;
  }

  function check(string, char) {
    if (string.includes(char)) {
      console.log(`Valid`);
    } else {
      console.log(`Your username must contain ${char}.`);
    }
    return string;
  }
}