Random password generation in js/ts

generatePassword.ts

const arrayShuffle = (input: string[]): string[] => {
  let i = input.length;
  const arr: string[] = [...input];

  while (i != 0) {
    const ri = Math.floor(Math.random() * i);
    i--;
    [arr[i], arr[ri]] = [arr[ri], arr[i]];
  }

  return arr;
};

export const generatePassword = (length: number = 18) => {
  const chars = [];

  // printable ascii chars are 33 through 126
  for (let i = 33; i <= 126; i++) {
    const char = String.fromCharCode(i);

    let fill: number;
    switch (true) {
      case i >= 97 && i <= 122:
      case i >= 48 && i <= 57:
        // numbers & lower case letters
        fill = 3;
        break;
      case i >= 65 && i <= 90:
        // upper case letters
        fill = 2;
        break;
      default:
        // special chars
        fill = 1;
    }

    chars.push(...new Array(fill).fill(char));
  }

  const shuffled = arrayShuffle(chars);
  return shuffled.slice(0, length).join("");
};