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I want to log traffic on website. On every hit I want to generate unique Id that will will be stored in database. To generate unique Id I wrote below code, but some time I get same entry in database.

 timingVar = 'load_'+Date.now()+'_'+uniqueid();

//function used to generate unique number//
function uniqueid() {
    var ALPHABET = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
    var ID_LENGTH = 8;
    var rtn = '';
    for (var i = 0; i < ID_LENGTH; i++) {
      rtn += ALPHABET.charAt(Math.floor(Math.random() * ALPHABET.length));
    }
    return rtn;
}
Paul Fitzgerald
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Praveen D
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    This will be much more proper if you generate this IDs on the server. Set a session for each user, if that user is coming for the second time, then record it. – Relm Apr 27 '16 at 08:57
  • I have to use java script for unique id, what is the issue with my code. my code can produce duplicate id? – Praveen D Apr 27 '16 at 09:07
  • The problem with your code is simply that it doesn't guard against duplicates, and doesn't have nearly a large enough random field. That's **why** we have robust UUID algorithms. 36 ^ 8 is just not remotely a sufficient field to expect random picks from it to be unique, esp. not when working with the imperfect pseudo-random number generators in browsers. – T.J. Crowder Apr 27 '16 at 09:22
  • @PraveenD without more info, it's likely not your unique id code, but how you use it. You've got `Date.now` in the id so two requests need to be made at exactly the same time and get the same random number? Unlikely (but possible which is why you should look at the link from TJCrowder). **However** I think you'll find that even if you have a truly unique ID, you'll still get duplicates in the DB. ie is this another **XY Problem**. Do you log IP address as well? Are the duplicates from the same IP? Most important, is your `timingVar` a global? (as presented in the question). – freedomn-m Apr 27 '16 at 09:38
  • Essentially, I'm saying that you're likely to be overwriting your timingVar before you send it, so the 1st call gets the 2nd call's value and you get a duplicate. This could be caused by a global var or by a misunderstanding of a closure. Without all of your code, it's impossible to determine. – freedomn-m Apr 27 '16 at 09:39
  • As such, I don't think this is a duplicate of the linked – freedomn-m Apr 27 '16 at 09:40

1 Answers1

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Databases can be configured to use an auto generated unique value (mostly sequential numbers) for a column. You should not have to rely on javascript on the client to do this.

Lukas Schneider
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