Javascript to generate random password with specific number of letters [closed]

Answer 1

 var random=Math.random().toString(36).substring(7);//this gives you 7 alpha numeric characters.
 var timestamp =new Date().getTime();//this gives you epoch time
 var my_very_unique_password=(random+timestamp);//concat both..
 alert(my_very_unique_password);

Fiddle http://jsfiddle.net/bP57B/

And if you dont want such huge passwords,just do alert(random)

Answer 2

Since a password needs to be unpredictable, it needs to be generated by a well seeded crypto PRNG. Math.random is usually not secure.

Modern browsers (At least the current versions of Firefox and Chrome) support window.crypto.getRandomValues which generates secure random values.

Presto based Opera doesn't support it, but its Math.random is secure. But since Opera has died, the fallback shouldn't be necessary anymore.

function randomString(length)
{
    var charset = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
    var i;
    var result = "";
    var isOpera = Object.prototype.toString.call(window.opera) == '[object Opera]';
    if(window.crypto && window.crypto.getRandomValues)
    {
        values = new Uint32Array(length);
        window.crypto.getRandomValues(values);
        for(i=0; i<length; i++)
        {
            result += charset[values[i] % charset.length];
        }
        return result;
    }
    else if(isOpera)//Opera's Math.random is secure, see http://lists.w3.org/Archives/Public/public-webcrypto/2013Jan/0063.html
    {
        for(i=0; i<length; i++)
        {
            result += charset[Math.floor(Math.random()*charset.length)];
        }
        return result;
    }
    else throw new Error("Your browser sucks and can't generate secure random numbers");
}

alert(randomString(10))

http://jsfiddle.net/ebbpa/