Question

In JavaScript typeof is an operator and a function. Is it better used as an operator or a function? Why?

Answer 1

typeof is an operator. You can easily check it using:

typeof(typeof)

Were typeof a function, this expression would return 'function' string, but it results in a syntax error:

js> typeof(typeof);
typein:8: SyntaxError: syntax error:
typein:8: typeof(typeof);
typein:8: .............^

so, typeof cannot be a function. Probably parenthesis-notation typeof(foo) made you think typeof is a function, but syntactically, those parenthesis are not function call – they are those used for grouping, just like (2 + 3) *2. In fact, you can add any number of them you want:

typeof(((((foo))))); // is equal to typeof foo;