Question

What does the isNaN() function?

Answer 1

The isNan() function returns true if the variable value is not a number. For example:

1. function number(num) {  
2.   if (isNaN(num)) {  
3.     return "Not a Number";  
4.   }  
5.   return "Number";  
6. }  
7. console.log(number('1000F'));  
8. // expected output: "Not a Number"  
9.   
10. console.log(number('1000'));  
11. // expected output: "Number"