create a random integer unique in a given array

Question

<div id='passarr'>1572 4528 3564 8921 4521</div>

I need to create a new random integer (4 digits), unique regarding the above content.

js

var content = $('#passarr').text();
var passarr = content.split(' ');
var pass = Math.floor(Math.random() * 9000) + 1000;
var i = 0;
while (i == 0) {
    if (jQuery.inArray(pass, passarr) > -1) {
        var pass = Math.floor(Math.random() * 9000) + 1000;
        i = 1;
    }
}

seems it works, but not sure this is the right and shortest way.
any suggestion?

It looks like the boolean expression in your if statement should actually be the boolean expression in the while statement. You don't need i. — castletheperson
– castletheperson, Commented Jul 28, 2017 at 17:37
I think what @4castle meant was while (jQuery.inArray(pass, passarr) === -1)) { ... } — Rob M.
– Rob M., Commented Jul 28, 2017 at 17:41
This works by luck. In (5/9000)**2 cases, it wont work... ;0 — Jonas Wilms
– Jonas Wilms, Commented Jul 28, 2017 at 17:44

Jonas Wilms · Accepted Answer · 2017-07-28 17:46:45Z

3

Your code is the way to go. However, you can eliminate a few smaller mistakes ( an unneccessary i and non working code in < 0.00001%) :

var content = $('#passarr').text();
var passarr = content.split(' ');
do {
  var pass = Math.floor(Math.random() * 9000) + 1000;
} while (jQuery.inArray(pass, passarr) > -1);

console.log(pass);

answered Jul 28, 2017 at 17:46

Jonas Wilms

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3 Comments

castletheperson Over a year ago

This is exactly the algorithm they need. My only suggestion is to move the declaration of var pass to be outside of the loop, so that someone who isn't aware of hoisting won't be confused by the scope of pass.

Jonas Wilms Over a year ago

@4castle thats actually a point for not changing it. Theyll wonder that this works, and will be more clever afterwards ;)

qadenza Over a year ago

excellent, later I saw that my code in fact doesn't work. This works. thanks a lot.

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