javascript - 为什么全局范围内的变量被分配给窗口对象？

Question

var foo = 'bar';
console.log(window.foo); // bar

似乎变量作为属性分配给 this，但在匿名函数中，this 引用父作用域，但不会将变量分配给父作用域。

function() {
    var foo = 'bar';
}();

window.foo; // undefined

变量在非全局范围内分配给什么对象？

Answer 1

引用http://perfectionkills.com/understanding-delete/#execution_context :

Every execution context has a so-called Variable Object associated with it. Similarly to execution context, Variable object is an abstract entity, a mechanism to describe variable instantiation. Now, the interesing part is that variables and functions declared in a source text are actually added as properties of this Variable object.

When control enters execution context for Global code, a Global object is used as a Variable object. This is precisely why variables or functions declared globally become properties of a Global object

然而，这些可变对象是不可访问的。唯一的非内部对象是全局对象、window 或 this(在全局上下文中)。

规范中的相关部分是#10: Executable Code and Execution Contexts .