The objects in the function object's [[scope]] property are copied into the scope chain in the same order.
首先将函数对象[[scope]]内部属性中的对象，按顺序复制到作用域链中。
When the function exits, the call object is removed from the scope chain.
在函数退出时，调用对象就会从作用域链中去掉。
When no nested functions are involved, the scope chain is the only reference to the call object.
如果不涉及到内嵌函数，这个作用域链是唯一引用到调用对象的。
Global variables are always the slowest to access because they are always last in the scope chain.
全局变量总是最慢的，因为它们总是位于作用域链的最后一环。
Local variables are faster to access than out-of-scope variables because they exist in the first variable object of the scope chain.
局部变量比域外变量快，因为它位于作用域链的第一个对象中。
Local variables are faster to access than out-of-scope variables because they exist in the first variable object of the scope chain.
局部变量比域外变量快，因为它位于作用域链的第一个对象中。
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