🔰scope chain

JS ⟩ concepts ⟩ scope ⟩ scope chain

when a module/function/block is defined, a new scope is created. The positioning of scopes nested inside one another creates a scope hierarchy called the scope chain.

⭐️ 重點

The scope of a code block can reach all its parent's lexical environment so it can use its parent’s variable(s). In this way, we have a scope chain, chain of all parent’s scope.

👥 相關

• lexical environment

• scope

• lexical environment vs. scope

• lexical scope - static scope

• execution context

🔴 主題

• LHS reference - find the variable container itself (in the scope chain).

📗 參考

• YDKJS: Scope & Closures (v.2) ⟩ Chapter 3: The Scope Chain

• Anil ⟩ Scope, Lexical Environment and Scope Chain in JavaScript ⭐️

❓

Q：lexical environment === scope❓

A：my understanding is that

• (global/module/function/block) scope is determined at compile-time.

• lexical environment is created at runtime, every time a scope is entered❗