checking for numbers

res, or something else entirely

[natty]

hi all ,

im looking for a little check for a number function
at the moment i have this

function isInteger(s){
var bad=false;
var c;
for (x=0;x<s.length;x++){
c = s.charAt(x);
if (c.match(/[0-9]/) == null ¦¦ c.match(/[.]/) ==null) {
bad=true;
break;
}
}
return bad;
}

which i hope should accept decimals too
any better ideas?

tia

nat

[Bernard Marx]

<* changed *>

I think this is working now...

If we're testing for numbers, we might as well get the number too.

1. Convert the string (or number) to a decimal number with the Number constructor as converter (not parseFloat, since it accepts trailing non-digits).
2. Number (and parseFloat) accept hex (0xnn) numbers, so we test to see if we would have got the same with parseFloat with explicit base 10.
3. The if comparison works for 'obviously' non-numbers because

[blue]NaN!= NaN[/blue]

4. After the function has returned, we test with!isNaN, not!= false, otherwise zero would not be considered a number.

function getNumber(str)
{
  var num = Number(str);
  if( parseFloat(str,10)==num )
    return num;
  else
    return Number.NaN;
}
//eg:
var str = "0x3" 
// str = "0x34" // reject hex
// str = "034" // parse lead zeros as decimal
// str = "0" // zero is a number
var num = getNumber(str)
if(!isNaN(num))
  alert(num)
else
  alert("not a number")

[natty]

hi ,

cheers bernard.. to the rescue as ever..
i had completely forgotten about parseFloat..

many thanks as always for your comtinued help :)