generate random string for div id

I want to display YouTube videos on my website, but I need to be able to add a unique id for each video that's going to be shared by users. So I put this together, and I have run into a little problem. I am trying to get the JavaScript to add a random string for the div id, but it's not working, showing the string:

<script type='text/javascript' src='jwplayer.js'></script>
<script type='text/javascript'>
function randomString(length) {
    var chars = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXTZabcdefghiklmnopqrstuvwxyz'.split('');
    
    if (! length) {
        length = Math.floor(Math.random() * chars.length);
    }
    
    var str = '';
    for (var i = 0; i < length; i++) {
        str += chars[Math.floor(Math.random() * chars.length)];
    }
    return str;
}

var div = randomString(8);
</script>

<div id='div()'>This text will be replaced</div>

<script type='text/javascript'>
  jwplayer('div()').setup({
    'flashplayer': 'player.swf',
    'file': 'http://www.youtube.com/watch?v=4AX0bi9GXXY',
    'controlbar': 'bottom',
    'width': '470',
    'height': '320'
  });
</script>

I really like this function:

function guidGenerator() {
    var S4 = function() {
       return (((1+Math.random())*0x10000)|0).toString(16).substring(1);
    };
    return (S4()+S4()+"-"+S4()+"-"+S4()+"-"+S4()+"-"+S4()+S4()+S4());
}

From https://stackoverflow.com/questions/105034/how-to-create-a-guid-uuid-in-javascript

2018 edit: I think this answer has some interesting info, but for any practical applications you should use Joe's answer instead.

A simple way to create a unique ID in JavaScript is to use the Date object:

var uniqid = Date.now();

That gives you the total milliseconds elapsed since January 1st 1970, which is a unique value every time you call that.

The problem with that value now is that you cannot use it as an element's ID, since in HTML, IDs need to start with an alphabetical character. There is also the problem that two users doing an action at the exact same time might result in the same ID. We could lessen the probability of that, and fix our alphabetical character problem, by appending a random letter before the numerical part of the ID.

var randLetter = String.fromCharCode(65 + Math.floor(Math.random() * 26));
var uniqid = randLetter + Date.now();

This still has a chance, however slim, of colliding though. Your best bet for a unique id is to keep a running count, increment it every time, and do all that in a single place, ie, on the server.

Here is the reusable function to generate the random IDs :

function revisedRandId() {
	 return Math.random().toString(36).replace(/[^a-z]+/g, '').substr(2, 10);
}

// It will not start with the any number digit so it will be supported by CSS3

I think some folks here haven't really focused on your particular question. It looks like the problem you have is in putting the random number in the page and hooking the player up to it. There are a number of ways to do that. The simplest is with a small change to your existing code like this to document.write() the result into the page. I wouldn't normally recommend document.write(), but since your code is already inline and what you were trying do already was to put the div inline, this is the simplest way to do that. At the point where you have the random number, you just use this to put it and the div into the page:

var randomId = "x" + randomString(8);
document.write('<div id="' + randomId + '">This text will be replaced</div>');

and then, you refer to that in the jwplayer set up code like this:

jwplayer(randomId).setup({

And the whole block of code would look like this:

<script type='text/javascript' src='jwplayer.js'></script>
<script type='text/javascript'>
function randomString(length) {
    var chars = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghiklmnopqrstuvwxyz'.split('');

    if (! length) {
        length = Math.floor(Math.random() * chars.length);
    }

    var str = '';
    for (var i = 0; i < length; i++) {
        str += chars[Math.floor(Math.random() * chars.length)];
    }
    return str;
}

var randomId = "x" + randomString(8);
document.write('<div id="' + randomId + '">This text will be replaced</div>'); 

  jwplayer(randomId).setup({
    'flashplayer': 'player.swf',
    'file': 'http://www.youtube.com/watch?v=4AX0bi9GXXY',
    'controlbar': 'bottom',
    'width': '470',
    'height': '320'
  });
</script>

---

Another way to do it

I might add here at the end that generating a truly random number just to create a unique div ID is way overkill. You don't need a random number. You just need an ID that won't otherwise exist in the page. Frameworks like YUI have such a function and all they do is have a global variable that gets incremented each time the function is called and then combine that with a unique base string. It can look something like this:

var generateID = (function() {
    var globalIdCounter = 0;
    return function(baseStr) {
        return(baseStr + globalIdCounter++);
    }
})();

And, then in practical use, you would do something like this:

var randomId = generateID("myMovieContainer");  // "myMovieContainer1"
document.write('<div id="' + randomId + '">This text will be replaced</div>');
jwplayer(randomId).setup({

i like this simple one:

function randstr(prefix)
{
	return Math.random().toString(36).replace('0.',prefix || '');
}

since id should (though not must) start with a letter, i'd use it like this:

let div_id = randstr('youtube_div_');

some example values:

youtube_div_4vvbgs01076
youtube_div_1rofi36hslx
youtube_div_i62wtpptnpo
youtube_div_rl4fc05xahs
youtube_div_jb9bu85go7
youtube_div_etmk8u7a3r9
youtube_div_7jrzty7x4ft
youtube_div_f41t3hxrxy
youtube_div_8822fmp5sc8
youtube_div_bv3a3flv425

I also needed a random id, I went with using base64 encoding:

btoa(Math.random()).substring(0,12)

Pick however many characters you want, the result is usually at least 24 characters.

Based on HTML 4, the id should start from letter:

> ID and NAME tokens must begin with a letter ([A-Za-z]) and may be followed by any number of letters, digits ([0-9]), hyphens ("-"), underscores ("_"), colons (":"), and periods (".").

So, one of the solutions could be (alphanumeric):

  var length = 9;
  var prefix = 'my-awesome-prefix-'; // To be 100% sure id starts with letter

  // Convert it to base 36 (numbers + letters), and grab the first 9 characters
  // after the decimal.
  var id = prefix + Math.random().toString(36).substr(2, length);

Another solution - generate string with letters only:

  var length = 9;
  var id = Math.random().toString(36).replace(/[^a-z]+/g, '').substr(0, length);

A edited version of @jfriend000 version:

	/**
	 * Generates a random string
	 * 
	 * @param int length_
	 * @return string
	 */
	function randomString(length_) {
		
		var chars = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghiklmnopqrstuvwxyz'.split('');
		if (typeof length_ !== "number") {
			length_ = Math.floor(Math.random() * chars.length_);
		}
		var str = '';
		for (var i = 0; i < length_; i++) {
			str += chars[Math.floor(Math.random() * chars.length)];
		}
		return str;
	}

Or you could use Cripto since it's already built in(except in IE11, I swear these guys havent updated in years!)

> https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getRandomValues#Examples

var id = new Uint32Array(10);
window.crypto.getRandomValues(id);

I also found this: > https://gist.github.com/6174/6062387#gistcomment-3255605

let length = 32;
let id = crypto.randomBytes(length).toString("base64");

There's a lot of ways to do this, but for most people, there's no reason to reinvent the wheel :)

I would suggest that you start with some sort of placeholder, you may have this already, but its somewhere to append the div.

<div id="placeholder"></div>

Now, the idea is to dynamically create a new div, with your random id:

var rndId = randomString(8); 
var div = document.createElement('div');
div.id = rndId
div.innerHTML = "Whatever you want the content of your div to be";

this can be apended to your placeholder as follows:

document.getElementById('placeholder').appendChild(div);

You can then use that in your jwplayer code:

jwplayer(rndId).setup(...);

Live example: http://jsfiddle.net/pNYZp/

Sidenote: Im pretty sure id's must start with an alpha character (ie, no numbers) - you might want to change your implementation of randomstring to enforce this rule. (ref)

May I an share an intuitive way to generate a randomID ?

const getRandomID = (length: number) => {
    let text = '';
    const possible = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';

    for (let i = 0; i < length; i++) {
        text += possible.charAt(Math.floor(Math.random() * possible.length));
    }
    return text;
}

First. Assign an id to your div. Like this:

<div id="uniqueid">This text will be replaced</div>

After that, add inside your <script> tag following code:

Document.getElementById("uniqueid").id = randomString(8);

window.btoa(String.fromCharCode(...window.crypto.getRandomValues(new Uint8Array(5))))

Using characters except ASCII letters, digits, '_', '-' and '.' may cause compatibility problems, as they weren't allowed in HTML 4. Though this restriction has been lifted in HTML5, an ID should start with a letter for compatibility.

function id(prefix = '', length = 7) {
    let result = prefix;
    for(let i = 0; i < length; i++) {
        const random = Math.random();
        result += String.fromCharCode(Math.floor(random * 26) + (random < .5 ? 65 : 97));
    }
    return result;
}

a random number between 0 and 25 is generated then added to either 65 or 97. When added to 65 it will give you an ascii code for a capital letter and when added to 97, an ascii code for a small letter.

Here is an easy one liner:

const generateUniqueID = (idLength) => [...Array(idLength).keys()].map((elem)=>Math.random().toString(36).substr(2, 1)).join("")

Where all you do is enter the idLength and it will return a unique id of that length.

generateUniqueID(23)
    
>>>'s3y9uebzuo73ih79g0s9p2q' // Id of length 23

For generating random ids, you can also use the standard crypto API with its randomUUID() function which is available in node.js (>=v16.7.0) and all relevant browsers except Safari:

const uuid = crypto.randomUUID()
console.log(uuid)
// prints e.g. "7f3f4512-fcf9-45fe-b726-512bba403426"