You are not calling the function, you are passing a reference to setTimeout that calls it directly, without the obj. before the call.

@getify explains it flawlessly, there are 4 modes: new, obj., bind/apply/call and default (window or error in strict mode)

As nhpatt notes you're not actually calling obj.method here, you're passing it as an argument, which will be called at a later time.

Looking at a possible implementation of setTimeout makes it clearer:

  function setTimeout(func, delay) {
    // wait for the delay to complete..
    func();
  }

Here you can see that when the function is called there's nothing to the left of it.