从变量内联JavaScript函数调用

Question

I want to call a function inline from a variable, but respecting the case, when the variable is null / undefined or not a function.

var f;
if(typeof(f) == 'function') {
    f(); // don't get executed
}
f(); // this is of course not working, but it is executing

var fn = function() { console.warn('fn'); }
fn(); // working because fn is a function

Basically I want the if statement, with checking whether the variable is a function or not in one line.

I saw this and thought there has to something for undefined / non functions:

var screenSize = screen.width || 1024;

Answer 1

You can use a logical AND:

typeof f === 'function' && f();

The second operator is only evaluated if the first one is truish.