Make fixed length random number / string in JavaScript with sample codes

Pisuke

How to make the following in JavaScript…

  • Fixed length random numbers,
  • Fixed length random string,

This article explains how to do it in JavaScript with example codes.

Table of Contents
  1. Make fixed length random numbers
  2. Make fixed length string [a-zA-Z]
  3. Generate fixed length hex code
  4. Generate random binary string

Make fixed length random numbers

How to make random number with fixed length.

  • Ex1 : 276199428
  • Ex2 : 129498289

Create a random number generator function as follows :

function randomNumbers(length) {
  var result = '';
  var chars = '0123456789';
  var charsLength = chars.length;
  for ( var i = 0; i < length; i++ ) {
    result += chars.charAt(
      Math.floor(Math.random() * charsLength)
    );
  }
  return result;
}

Generate random numbers by using the above func :

/// Generate 5 length random numbers
randomNumbers(8);
  /// => '13432233'
randomNumbers(8);
  /// => '58069170'

/// Generate 20 length random numbers
randomNumbers(20);
  /// => '29678817177096512499'
randomNumbers(20);
  /// => '80786866995930267929'
randomNumbers(20);
  /// => '52494552172139615664'

Any-digit number can be generated.

Make fixed length string [a-zA-Z]

How to make fixed length string with fixed length.

  • Ex1 : ‘TrlTgzDyDm’
  • Ex2 : ‘HnFNoPMfeu’

Create a string generator function as follows :

function randomString(length) {
  var result = '';
  var chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
  var charsLength = chars.length;
  for ( var i = 0; i < length; i++ ) {
    result += chars.charAt(
      Math.floor(Math.random() * charsLength)
    );
  }
  return result;
}

Example usages of the above function :

/// Make 5 length random string
randomString(5);
  /// => 'a2FeC'
randomString(5);
  /// => 'we5M2'

/// Make 10 length random string
randomString(10);
  /// => 'UAZ2iKAUcm'
randomString(10);
  /// => 'BZKQRMQW8V'

Strings containing only letters [a-zA-Z] of fixed length are generated.

Generate fixed length hex code

Random hex numbers with fixed digits can also be generated.

Create a hex code generator function :

function randomHex(length) {
  let result = '';
  const chars = '0123456789abcdef';
  const charsLength = chars.length;
  for ( var i = 0; i < length; i++ ) {
    result += chars.charAt(
      Math.floor(Math.random() * charsLength)
    );
  }
  return result;
}

Make random hex code by the above func :

/// Make 6 length hex codes
randomHex(8);
  /// => '4ca9cd32'
randomHex(8);
  /// => 'fd7f679f'

/// Make 16 length hex codes
randomHex(16);
  /// => 'ff7198af24f25da3'
randomHex(16);
  /// => '0b4d19a0c7db1e04'
randomHex(16);
  /// => '3d9b4f71456c8ea9'

Generate random binary string

Create a binary string generator function :

function randomBin(length) {
  let result = '';
  const chars = '01';
  const charsLength = chars.length;
  for ( var i = 0; i < length; i++ ) {
    result += chars.charAt(
      Math.floor(Math.random() * charsLength)
    );
  }
  return result;
}

Make random binary strings by the above func :

/// Make 8 length binary strings
randomBin(8);
  /// => '11010100'
randomBin(8);
  /// => '11100111'
randomBin(8);
  /// => '00001001'

Other n-decimal systems (e.g., octal / ternary) can also be generated randomly with any number of digits by restricting the types of characters that can be included.

Leave a Reply