A leap year test program that detects whether the input is legitimate

1, leap years: where there is a leap year in the Gregorian calendar (February is 29th), the leap surplus (aged more than a leap. The lunar calendar is less than the year of the return year).

2, Leap Year Judgment method: four Years a leap, A.D. year can be divisible by 4 can not be divisible by 100, or can be divisible by 400 years.

3, because recently learning JavaScript, so now use javascript+html to implement this function, the code is as follows:

Run as follows:
4, it is simple to verify the following table shows:

 
 
 
  
  
 
   
 
    
User input
 
    
Expected results
 
    
Actual output
 
   
 
   
 
    
2012
 
    
Leap
 
    
Leap
 
   
 
   
 
    
2013
 
    
Not a leap year
 
    
Not a leap year
 
   
 
   
 
    
2013abc
 
    
Illegal input
 
    
Illegal input
 
   
 
   
 
    
Abch
 
    
Illegal input
 
    
Illegal input
 
   
 
  
 
 
 
Test 1:
Test 2:
Test 3:
Test 4:
Code Gameover, I went to write parallel computing homework, TA sister goodbye ...
A leap year test program that detects whether the input is legitimate