How To/webdev/

How to check NaN property in javascript

NaN stands for "Not a Number". To check if object is NaN you cannot use != or == comparison. NaN is not a Number or String. You have to use isNaN() function or !NaN.

x = parseFloat('1234.5');
y = parseFloat('abc');

alert(x); //1234.5
alert(y); //NaN

alert(x == false); //false
alert(y == false); //false

alert(x == true); //false
alert(y == true); //false

alert(!x); //false
alert(!y); //true - it works!

alert(typeof(y)); //number
alert(y == NaN); //false
alert(y == 'NaN'); //false
alert(isNaN(y)); //true - it works!