I was doing some work with numbers in JavaScript and stumbled upon this most interesting property.
isNaN()
=> true
isNaN(null)
=> false
parseFloat(null)
=> NaN
It would appear that the interpreter can’t make up it’s mind about what null actually is, never mind whether or not it’s a number. Combine this with the [in]famous JavaScript truth table and you have for a very loosely typed language.