parseInt is a function that converts a string into an integer. It stops when it sees a nondigit, so parseInt("16") and parseInt("16 tons") produce the same result. It would be nice if the function somehow informed us about the extra text, but it doesn't.

If the first character of the string is 0, then the string is evaluated in base 8 instead of base 10. In base 8, 8 and 9 are not digits, so parseInt("08") and parseInt("09") produce 0 as their result. This error causes problems in programs that parse dates and times. Fortunately, parseInt can take a radix parameter, so that parseInt("08", 10) produces 8. I recommend that you always provide the radix parameter.