var name = "the Window.";
var object = {
name:"Object",
getName: function(){
return this.name;
}
}
(object.getName)(); //"Object"
(object.getName = object.getName)(); //"the Window"
I run this code, and it return "the Window", while i think it should be "Object".Please tell me why? thanks.
var name = "the Window.";
Global declarations create a property of the global/window object. This is equivalent (more or less) to:
var global = this;
global.name = 'the Window';
The expression:
(object.getName = object.getName)
returns the function referenced by object.getName. The following empty parameter list (i.e. the ()) causes it to be called.
Since the this value is not set by the call, it defaults to the global/window object, so the function returns the value of global.name.
The bottom line of confusion is we are trying to execute
(object.getName = object.getName)();
and we think it should print "Object".
Actually, it won't. Here is a simple reason. If you break this statement into 2 statements you will get it.
Try this
var x = object.getName;
x();
It is somewhat similar to your case and it gives 'the window.' too for the same reason x is executed by window.
Instead of thinking of this in the classic OOP way you're used to, think of this as the context on which a function is called.
In your sample code, window is the context for the getName call, regardless of where that function is declared.
var x = object.getName;
x();
is not quite the same. the "=" only make sure that x refer to the same memory address as object.getName, but x belongs to window while object.getName belongs to object. I think the problem comes from the return value of the assignment expression. maybe there is a temporary variable to receive the value of (object.getName = object.getName), that is,
var temp = (object.getName = object.getName);
temp();//"the Window"
thus may make sense.
thismust definitely be the most talked about thing in SO.thisis undefined and not a fallback to the global context.