Javascript shorthand to call method if object exists

Question

I have a variable and if that variable is a object I would like to call a method on that object, if not I want to do nothing.

I'm wondering if there is any reason why I shouldn't do it like this.

var foo = null;

  ////////////////////////////////////////////////
  // some code that could change foo to a object
  ////////////////////////////////////////////////

 foo && foo.bar();

Answer 1

With ES6, you can combine optional chaining operator with call:

foo?.bar?.call()

If you want to pass arguments, keep in mind that the first one in call assigns this in function call

var foo = {
  bar: function(x) { return x; }
};

first.value  = foo?.bar?.call(0,42); // 42
second.value = foo?.baz?.call(0,42); // undefined, no error

<input id="first">
<input id="second">

Answer 2

The quick answer is yes, foo && foo.bar() won't throw an exception if foo is null, and if foo is non-null, bar() will be evaluated, and it's value will be the value of the expression.

Longer answer is that any value can be interpreted as a boolean, in the sense that every value is either truthy or falsey, and that the boolean operators do short-circuit evaluation -- left to right, if we see a false && or a true ||, there's no reason to carry on evaluating.

One last fact is that the value of boolean expression is the value of the expression where the short-circuit happened.