Random number with fixed length

Question

I want to generate a random integer number with 0-9 numbers and with length = 5. I try this:

function genRand(min,max) {
    for (var i = 1; i <= 5; i++) {
        var range = max - min + 1;
        return Math.floor(Math.random()*range) + min;
    }
}

and call:

genRand(0,9);

But it always returns 1 number, not 5 (

Help please!

So, you want a random, 5-digit integer is what you are saying? It's not clear. — Nate B, Dec 12 '11 at 14:54
generate randomly 5 single digits from 0 to 9 and paste them — skywind, Dec 12 '11 at 14:58
"paste"? Could you include some desired results of what you want the function to return? String "07198" or Array (Object) [0,7,1,9,8] ? — Stefan, Dec 12 '11 at 15:11

score 15 · Accepted Answer · answered Dec 12 '11 at 14:57

15

   function genRand() {
      return Math.floor(Math.random()*89999+10000);
   }

answered Dec 12 '11 at 14:57

Nate B

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Why do you use 89999? – Oscar López Oct 21 '16 at 14:46
2

Math.random returns a random number between 0 (inclusive) and 1 (exclusive). Therefore you could instead do Math.floor(Math.random() * 90000) + 10000 as you're guaranteed never to generate 90000. – k2snowman69 Jul 06 '17 at 22:10
@OscarLópez 89999 comes from the maximum 5 digit number possible (99999) - the lowest 5 digit number possible (10000) – k2snowman69 Jul 06 '17 at 22:11

score 9 · Answer 2 · answered Dec 12 '11 at 14:54

9

return exits the function on the first loop.

answered Dec 12 '11 at 14:54

graphicdivine

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score 2 · Answer 3 · answered Feb 02 '17 at 03:30

2

Here's a more generalized version of Nate B's answer:

function rand(digits) {
    return Math.floor(Math.random()*parseInt('8' + '9'.repeat(digits-1))+parseInt('1' + '0'.repeat(digits-1)));
}

answered Feb 02 '17 at 03:30

Jacob

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kennebec · Answer 4 · 2011-12-12T15:34:03.500

2

The smallest 5 digit number is 10000, the largest is 99999, or 10000+89999.

Return a random number between 0 and 89999, and add it to the minimum.

var ran5=10000+Math.round(Math.floor()*90000)

Math.floor rounds down, and Math.random is greater than or equal to 0 and less than 1.

edited Dec 12 '11 at 15:34

answered Dec 12 '11 at 15:27

kennebec

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phoxis · Answer 5 · 2011-12-12T15:03:43.047

1

To get a 5 digit random number generate random numbers between the range (10000, 99999). Or generate randomly 5 single digits and paste them.

EDIT

The process you have shown simply will generate one number and return to the caller. The think which might work is (pseudo code) :

int sum = 0;
int m = 1;
for (i=0;i<5;i++)
{
  sum = sum  + m * random (0, 9);
  /*       or                  */
  sum = sum * m + random (0, 9);
  m = m * 10;
}

Or better generate 5 digit random numbers with rand (10000, 99999)

edited Dec 12 '11 at 15:03

answered Dec 12 '11 at 14:56

phoxis

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"generate randomly 5 single digits from 0 to 9 and paste them" YES! – skywind Dec 12 '11 at 14:57
1

isn't it better to simply generate random numbers within the range (10000, 99999) ?? For pasting the 5 randomly generated digits (0 to 9) you need to perform 5 multiplications and 5 additions. – phoxis Dec 12 '11 at 14:57

Random number with fixed length

5 Answers5

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