javascript If-Else语句跳过If条件

Question

As you can see in the picture the value of the r.SalaryGrade is null . Why it skip my IF condition and goes to Else ?. I make sure that if is an empty string and null it will add a class to a textbox. Did I do something wrong?.

 if (r.SalaryGrade == "" && r.SalaryGrade == null) { $("#JobGradeId").addClass('validation'); }
 else { $("#JobGradeId").removeClass('validation'); }

Answer 1

Your if condition has an "&&" in it.

'' and null are different things

You need to change how you structure that if statement. You could do something like,

r.SalaryGrade == "" || r.SalaryGrade == null

Answer 2

r.salaryGrade = "" as the first conditional passed, therefore it cannot be equal to null ( as it HAS a value of "" which is not null ).

You can change the && to an || and if either is true it will continue on.

Answer 3

As there is && in the if statement. it does not go in the if statement. Just try this for clarification- just make an if statement

String s= "";

IF(s == null) print "it is null";

else print "it is not null";

See yourself whether String s can be empty and null at the same time.