Javascript：何时创建范围链？

问题描述

我听到两种说法：

定义函数时：

• 在>第7章：函数表达式闭包部分中< Web开发人员专业JavaScript，第3版>

• 创建阶段[当函数被调用时，但在它执行任何内部代码之前]：
  
  
  
  • 创建变量，函数和参数
  
  
  • 创建范围链。
  
  
  • 确定this的值。
    
>激活/代码执行阶段：



• 分配值，对函数的引用以及解释/执行代码





据说范围链是在函数被调用时创建的。




那么哪个是正确的？

解决方案

函数有一个内部的[[Scope]]属性，该函数在中定义时定义。





该范围是范围链的一部分，与当创建新范围时一起该功能被执行。


I heard two kinds of saying:

When function is defined:

• In book Professional Javascript for Web Developers, 3rd Edition, in the Chapter 7: Function Expressions Closures parts:

it's said the scope chain is created when the function id defined.

When function is called:

• In this article: What is the Execution Context & Stack in JavaScript?:
• Creation Stage [when the function is called, but before it executes any code inside]:
  • Create variables, functions and arguments.
  • Create the Scope Chain.
  • Determine the value of "this".
• Activation / Code Execution Stage:
  • Assign values, references to functions and interpret / execute code.

it's said the scope chain is created when the function is called.

So which is right ?

解决方案

Functions have an internal [[Scope]] property which is set to the scope where the function is defined in, when it is defined.

That scope is then part of the scope chain, together with the new scope created when the function is executed.

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