函数表达式的上下文变为 window

gistfile1.txt

var hooks = {
	foo: function() {
		console.log(this)
	},
	_default: function() {
		console.log(this)
	}
}

owner.foo() // hooks
owner['foo']() // hooks
(owner['foo'])() // hooks
(owner['foo'] || owner._default)() // window
(owner['bar'] || owner._default)() // window