isNaN function
The isNaN function checks if
a passed parameter is a number or
not. It returns true if the
parameter is not a number and
false if it is. How it
works: the passed parameter is
converted to a number. If it is not
a number (string, array, etc.),
then it is converted to
NaN.
Well, and isNaN checks whether we
got NaN after conversion or not. But
true is converted not to NaN,
but to the number 1. There are other
similar pitfalls, see them in the
NaN
description.
Syntax
isNaN(value);
Example
Now isNaN will return
false since the parameter
is a number:
console.log(isNaN(3));
The code execution result:
false
Example
Now isNaN will return
true since the parameter
is not a number:
console.log(isNaN('abcde'));
The code execution result:
true