What does isNaN function behave in Javascript?

Answer:

It's a javascript in-built function which returns true,if expression or argument is not a number otherwise returns false.
Full form of isNan is Not a number.

For Example:-

document.write(isNaN("Vishal")+ "</br>");

document.write(isNaN("2013/12/10")+ "</br>");

document.write(isNaN(123)+ "</br>");

Output will be:-

true
true
false