Generate a random alphanumeric JavaScript string

While generating a random arithmetic or boolean value is fairly easy in JavaScript, generating a random alphanumeric string is a bit more involved.

In order to generate a random alphanumeric string, you can use Math.random() to generate a random floating-point number and then convert it to a string using Number.prototype.toString() with a radix value of 36. This will convert the number to an alphanumeric string.

As this string will be of variable length, you need to repeat the process as many times as required, up to the specified length. This is where Array.from() and Array.prototype.some() come in handy. Generating an array of length and repeating until the desired length is reached allows us to only run as many steps as necessary.

Finally, you can use String.prototype.slice() to trim down the generated string if it's longer than the given length.

const randomAlphaNumeric = length => {
  let s = '';
  Array.from({ length }).some(() => {
    s += Math.random().toString(36).slice(2);
    return s.length >= length;
  });
  return s.slice(0, length);
};

randomAlphaNumeric(5); // '0afad'