How to generate short uid like “aX4j9Z” (in JS)

Question

For my web application (in JavaScript) I want to generate short guids (for different objects - that are actually different types - strings and arrays of strings)

I w

Answer 1

You can use the md5 algorithm for generating a random string. md5 is the node package

 var randomChars = Math.random().toString(36).replace(/[^a-z]+/g, '').substr(0, 2);
 var shortUrl = md5(originalUrl + randomChars + new Date()).substring(0, 5).toString();
 console.log(shortUrl);

This will generate unique string every time.

Answer 2

just randomly generate some strings:

function getUID(len){
    var chars = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789',
          out = '';

    for(var i=0, clen=chars.length; i<len; i++){
       out += chars.substr(0|Math.random() * clen, 1);
    }

    // ensure that the uid is unique for this page
    return getUID.uids[out] ? getUID(len) : (getUID.uids[out] = out);
}
getUID.uids = {};

Answer 3

You can shorten a GUID to 20 printable ASCII characters without losing information or the uniqueness of the GUID.

Jeff Atwood blogged about that years ago:
Equipping our ASCII Armor

Answer 4

The following generates 62^3 (238,328) unique values of 3 characters provided case sensitivity is unique and digits are allowed in all positions. If case insensitivity is required, remove either upper or lower case characters from chars string and it will generate 35^3 (42,875) unique values.

Can be easily adapted so that first char is always a letter, or all letters.

No dobut it can be optimised, and could also refuse to return an id when the limit is reached.

var nextId = (function() {
  var nextIndex = [0,0,0];
  var chars = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'.split('');
  var num = chars.length;

  return function() {
    var a = nextIndex[0];
    var b = nextIndex[1];
    var c = nextIndex[2];
    var id = chars[a] + chars[b] + chars[c];

    a = ++a % num;

    if (!a) {
      b = ++b % num; 

      if (!b) {
        c = ++c % num; 
      }
    }
    nextIndex = [a, b, c]; 
    return id;
  }
}());

Answer 5

Get a simple counter to start from 100000000, convert the number into radix 36.

(100000000).toString(36);  //1njchs

(2100000000).toString(36); //yqaadc

You can comfortably have 2 billion elegant unique ids, just like YouTube

Answer 6

Update 08/2020:

shortid has been deprecated in favor of nanoid which is smaller and faster:

• Small. 108 bytes (minified and gzipped). No dependencies. Size Limit controls the size.
• Fast. It is 40% faster than UUID.
• Safe. It uses cryptographically strong random APIs. Can be used in clusters.
• Compact. It uses a larger alphabet than UUID (A-Za-z0-9_-). So ID size was reduced from 36 to 21 symbols.
• Portable. Nano ID was ported to 14 programming languages.

import { nanoid } from 'nanoid'

// 21 characters (default)
// ~149 billion years needed, in order to have a 1% probability of at least one collision.
console.log(nanoid()) //=> "V1StGXR8_Z5jdHi6B-myT"

// 11 characters
// ~139 years needed, in order to have a 1% probability of at least one collision.
console.log(nanoid(11)) //=> "bdkjNOkq9PO"

More info here : https://zelark.github.io/nano-id-cc/

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Old answer

There is also an awesome npm package for this : shortid

Amazingly short non-sequential url-friendly unique id generator.

ShortId creates amazingly short non-sequential url-friendly unique ids. Perfect for url shorteners, MongoDB and Redis ids, and any other id users might see.

• By default 7-14 url-friendly characters: A-Z, a-z, 0-9, _-
• Non-sequential so they are not predictable.
• Supports cluster (automatically), custom seeds, custom alphabet.
• Can generate any number of ids without duplicates, even millions per day.
• Perfect for games, especially if you are concerned about cheating so you don't want an easily guessable id.
• Apps can be restarted any number of times without any chance of repeating an id.
• Popular replacement for Mongo ID/Mongoose ID.
• Works in Node, io.js, and web browsers.
• Includes Mocha tests.

Usage

var shortid = require('shortid');
console.log(shortid.generate()); //PPBqWA9