Why does Javascript parseInt('0x4A') return the same as parseInt('0x4Avv')?

Question

Why does Javascript parseInt('0x4Avv') return the same as parseInt('0x4A') I was counting on parseInt('0x4Avv') to return NaN.

Is there anyway to make it behave as such?

Even weird strings 'work', e.g: parseInt('0x4Av--9-0-90v') yields the same result as parseInt('0x4A')

Observed in all browsers....

Answer 1

Here is an excerpt from the MDN parseInt documentation

If parseInt encounters a character that is not a numeral in the specified radix, it ignores it and all succeeding characters and returns the integer value parsed up to that point. parseInt truncates numbers to integer values. Leading and trailing spaces are allowed.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/parseInt

There isn't a built in way to make it behave otherwise, but you could conceivably write your own int parsing function using regex that could be more strict.