[thelist] javascript numbers with decimals

Ken Snyder kendsnyder at gmail.com
Wed May 7 09:37:56 CDT 2008

Joshua Olson wrote:
>> Since you can enter in 544.44.44 with this, I might also have 
>> a isNaN  
>> check afterwards.  dunno if that is the best tactic, but clearly I  
>> don't do a ton of work in js.
> This is the crux.  We need a well designed regex if we really want to ensure
> our input is good.  Sometimes it's better to check to see if the input
> matches the format of what we expect, and then allow the user to fix the
> information instead of trying to manipulate the provided information until
> it matches what we expect (as the original code does).  
Forget the regex--why not just compare the float-cast version to the 
string version?

function isValidNumber(str) {
  return parseFloat(str) == str;

isValidNumber('521.44'); // true
isValidNumber(521.44); // true
isValidNumber('.44'); // true
isValidNumber('521.4'); // true
isValidNumber('$521'); // false
isValidNumber('52o'); // false
isValidNumber('544.44.44'); // false

- Ken Snyder

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