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JavaScript JavaScript Foundations Functions Return Values

Posted by Jerry Liu
Jerry Liu
Courses Plus Student 1,233 Points

Why is this condition always true?

 function arrayCounter (my_var) {
        if (typeof my_var === ('number'|'string'|'undefined')) return 0;
        else return my_var.length;
      }

arrayCounter();

1 Answer

Dino Paškvan
PLUS
Dino Paškvan
Courses Plus Student 44,108 Points
Dino Paškvan
Dino Paškvan
Courses Plus Student 44,108 Points

That condition is not always true. In fact, it's never true. The else statement will always get executed. A single pipe character (|) is not the logical or operator. It's a bitwise or operator, and as such, it only works on numbers (and not in the way you'd expect a logical or to work).

So, this part of the code: ('number'|'string'|'undefined') will always return 0, because you are trying to use bitwise operators on a string. The typeof operator will never return 0, and because of that, the if condition will never pass. Instead, the code in the else block is executed.

If you want to understand how the logical or works, take a look at this thread.