That was my potential complaint/fix #1: that parseInt could refuse to work if it is passed a string that contains things that aren't valid digits in whatever radix it is working in. I personally believe I agree with you, but this is actually the way these functions work in most languages. In particular, this is the behavior of the various functions in C, such as atoi and strtol. While this isn't then "best of breed" behavior, I don't think it is unreasonable behavior. (Python's int() does not do this, for what it is worth: it gets angry and throws an exception if you pass it something that isn't entirely a number.)