I'm looking for an efficient, elegant way to generate a JavaScript variable that is 9 digits in length:
Example: 323760488
+3
A:
You could generate 9 random digits and concatenate them all together.
Or, you could call random() and multiply the result by 1000000000:
Math.floor(Math.random() * 1000000000);
Since Math.random() generates a random double precision number between 0 and 1, you will have enough digits of precision to still have randomness in your least significant place.
If you want to ensure that your number starts with a nonzero digit, try:
Math.floor(100000000 + Math.random() * 900000000);
Or pad with zeros:
function LeftPadWithZeros(number, length)
{
var str = '' + number;
while (str.length < length) {
str = '0' + str;
}
return str;
}
Or pad using this inline 'trick'.
ggg
2010-08-09 03:21:25
AnApprentice
2010-08-09 03:21:49
How would that be 9 digits in length? 9 digits needs to be a fixed length never more or less
AnApprentice
2010-08-09 03:23:09
just need to handle cases like 0.000001234, pad with zeros up to 9 digits
Mitch Wheat
2010-08-09 03:24:18
@nobosh: 0 is a valid digit, even on the left side of your number. If you wanted a number >= 100000000, then you would have to say so (I've updated my answer to cover this case).
ggg
2010-08-09 03:24:38
convert the resulting number to a string. Pad with zeroes on left if length < 9. Zeroes are perfectly good random numbers and should not suffer discrimination!
Larry K
2010-08-09 03:27:16
@nobosh: It depends, are leading zeros allowed? For example, is `000000001` a valid number?
slebetman
2010-08-09 03:27:30
A:
Start with the smallest 10-digit number, then subtract off a random number less than 1,000,000,000. Like so:
1000000000 - Math.floor(Math.random() * 1000000000);
Zach Rattner
2010-08-09 03:30:13
A:
why don't just extract digits from the Math.random() string representation?
Math.random().toString().slice(2,11);
/*
Math.random() -> 0.12345678901234
.toString() -> "0.12345678901234"
.slice(2,11) -> "123456789"
*/
(requirement is that every javascript implementation Math.random()'s precision is at least 9 decimal places)
mykhal
2010-08-09 03:38:32