How to Generate a random number of fixed length using JavaScript?

Question

I\'m trying to generate a random number that must have a fixed length of exactly 6 digits.

I don\'t know if JavaScript has given below would ever create a number less th

Answer 1

I was thinking about the same today and then go with the solution.

var generateOTP = function(otpLength=6) {
  let baseNumber = Math.pow(10, otpLength -1 );
  let number = Math.floor(Math.random()*baseNumber);
  /*
  Check if number have 0 as first digit
  */
  if (number < baseNumber) {
    number += baseNumber;
  }
  return number;
};

Let me know if it has any bug. Thanks.

Answer 2

You can use this module https://www.npmjs.com/package/uid, it generates variable length unique id

uid(10) => "hbswt489ts"
 uid() => "rhvtfnt" Defaults to 7

Or you can have a look at this module https://www.npmjs.com/package/shortid

const shortid = require('shortid');

console.log(shortid.generate());
// PPBqWA9

Hope it works for you :)

Answer 3

This is another random number generator that i use often, it also prevent the first digit from been zero(0)

  function randomNumber(length) {
    var text = "";
    var possible = "123456789";
    for (var i = 0; i < length; i++) {
      var sup = Math.floor(Math.random() * possible.length);
      text += i > 0 && sup == i ? "0" : possible.charAt(sup);
    }
    return Number(text);
  }

Answer 4

More generally, generating a random integer with fixed length can be done using Math.pow:

var randomFixedInteger = function (length) {
    return Math.floor(Math.pow(10, length-1) + Math.random() * (Math.pow(10, length) - Math.pow(10, length-1) - 1));
}

To answer the question: randomFixedInteger(6);