@marcelgerber This is an interesting case. Due to the regex used to parse the cubic-bezier string, the last value is "everything past the 3rd comma and past whitespace". So there could be a lot of weird stuff in here -- too much I think to try to parse with our own regex.

So, I looked at the code that currently traps the exception and it's using the unary operator to convert from string to number. I think we still need parseFloat to make sure it's a base 10 number, but this code seems to be simpler, solve the problem, and all unit tests still work:

        if (typeof str !== "string") {
            return { isNumber: false, value: null };
        }
        var val = parseFloat(+str, 10),
            isNum = (typeof val === "number") && !isNaN(val) &&
                    (val !== Infinity) && (val !== -Infinity);

What do you think of this solution?

Yay! Unit test!