Valid number?

[davej]

I'm having a problem in Chrome with some navigation values causing exceptions to be thrown when .toFixed is used on them. I am now trying to use...

temp = position.coords....if (temp != null && Number(temp) != NaN)data += temp.toFixed(8);

But this isn't working 100% either, at least not in Firefox. What is the best way to screen for invalid numbers?

Edited December 26, 2012 by davej

[Ingolme]

You can use a regular expression to check that only numbers are used.

if(!/[0-9]+(\.?[0-9])?/.test(str)) {	alert("Number not valid.");}

[davej]

I thought that was the whole point of the Number() function? Oh, I think I solved it using isNaN() http://www.w3schools.com/jsref/jsref_isnan.asp

Edited December 27, 2012 by davej

[Ingolme]

The point of Number() isn't to validate numbers, but to cast to a number.When casting to number, as long as the first character is numeric it is considered a number and it will continue to parse until it finds a non.numeric character. Now that I think of it, NaN is never equal to another NaN. The only way to check that a "number" is not a number is to use isNaN().

[davej]

So really the best test would be? if ( isNaN( Number(x) ) ) {alert('NaN');}

[Ingolme]

That should work. However, if x is "5abc" it will evaluate to 5 and be a number. If you're fine with that then your script is OK.

[davej]

Yes, I've run into that before. Is there a scheme that would reject "5abc" ?

[Ingolme]

A regular expression would, which is what I provided earlier.

[boen_robot]

Why would you reject that if you can just use the number value though?I mean, you can simply do:

x = new Number(x);if (!isNaN(x)) {    //No problem. Continue with "x", that is now surely a valid number.}

[Ingolme]

Perhaps it's validation before passing to the server-side. PHP casts to numbers using the same rules as Javascript using (int) or intval(), (float) or floatval()

[davej]

If a user entered 5abc you might want to reject it simply because a number was expected and they entered something goofy. I had not thought of using a regex for that purpose. Thanks.