What is the meaning of NaN??

Answer 1

NaN means Not a Number. However it is necessarily not a char or bool or something else. Thats only the case with parseInt function.

NaN is a built in object which turns up if you did something that should not be a valid no.
Eg.

0/0
"hello"-5
parseInt("hello")
undefined+1

Btw, NaN belongs to the primitive type number.

Answer 2

"Not a Number"
It could be a char or a boolean or something else!

Examples:
alert(parseInt("A string")); // alerts NaN
alert(parseInt(true)); // alerts NaN

Answer 3

http://lmgtfy.com/?q=What+is+the+meaning+of+NaN%3F+Programming