Check if character is number?

You could use comparison operators to see if it is in the range of digit characters:

var c = justPrices[i].substr(commapos+2,1);
if (c >= '0' && c <= '9') {
    // it is a number
} else {
    // it isn't
}

you can either use parseInt and than check with isNaN

or if you want to work directly on your string you can use regexp like this:

function is_numeric(str){
    return /^\d+$/.test(str);
}

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.

Check if character is number?

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