Javascript shorthand to call method if object exists

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

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.