🔰variable hoisting

🚧 施工中

JS ⟩ scope ⟩ hoisting ⟩ variable hoisting

• var hoisting

  • identifier： hoisted to the top of its enclosing function scope. ( 👉 var has no block scope❗️❗)

  • value： initialized to undefined❗

• let/const/class hoisting

  • identifier： hoisted to the top of its scope.

  • value： uninitialized❗(referencing it before init causes ReferenceError)

⭐️ 重點

in the same scope, function hoisting has higher priority over variable hoisting. ( 👉 function hoisting first❗️❗)

🔴 主題

• var hoisting

• let/const/class hoisting

• related topics

  • variable declaration

👥 相關

• compare： function hoisting

📗 參考

• YDKJS: Scope & Closures (v.2) ⟩

  • Ch. 1 ⟩ Hoisting

  • Ch. 5 ⟩ Hoisting: Declaration vs. Expression