Check if character is number?

Question

I need to check whether justPrices[i].substr(commapos+2,1).

The string is something like: \"blabla,120\"

In this case it would check whether \'0

Answer 1

EDIT: Blender's updated answer is the right answer here if you're just checking a single character (namely !isNaN(parseInt(c, 10))). My answer below is a good solution if you want to test whole strings.

Here is jQuery's isNumeric implementation (in pure JavaScript), which works against full strings:

function isNumeric(s) {
    return !isNaN(s - parseFloat(s));
}

The comment for this function reads:

// parseFloat NaNs numeric-cast false positives (null|true|false|"")
// ...but misinterprets leading-number strings, particularly hex literals ("0x...")
// subtraction forces infinities to NaN

I think we can trust that these chaps have spent quite a bit of time on this!

Commented source here. Super geek discussion here.