➕assignment (=)

JS ⟩ operator ⟩ assignment ⟩ =

(operator) assigns value to variable / property / element, and returns the assigned value.

⭐️ 重點

var redeclaration

• is ignored and won't trigger any error, even in strict mode❗

• ⭐️ the assignment (=) part is applied❗

👉 var redeclaration applied even in strict mode❗️

⭐️ assignment (=) to an undeclared identifier will result in

• ❗accidental global variable in sloppy mode❗️ in sloppy mode.

• 🛡️⛔️ ReferenceError'xxx' is not defined❗️strict mode

the assignment of a property always creates/sets a property in the original object, it never modifies objects in the prototype chain.

🔴 主題

• destructuring assignment

• dot notation (.) / bracket notation [] - assignment of a property

👥 相關

• strict equality (===)

• sloppy equality (==)

• lvalue is a term for variable / property / element.

📗 參考

• JavaScript: The Definitive Guide ⟩ 4.11 Assignment Expressions

📘 手冊

• Expressions and operators ⟩ assignment operators ⟩ Assignment (=)