❗var redeclaration applied even in strict mode❗️

• JS ⟩ variable ⟩ var ⟩ redeclaration applied

• JS ⟩ grammar ⟩ declaration ⟩ redeclaration ⟩ var redeclaration applied

var redeclaration

• the declaration part is ignored ❗

• ⭐️ the assignment (=) part is applied❗

• won't trigger any Error ( even in strict mode❗)

⭐️ 重點

JS is lenient with var, strict with let.

• var redeclaration applied even in strict mode❗️

• let redeclaration not allowed even in sloppy mode❗️

👥 相關

• ✅let redeclaration not allowed even in sloppy mode❗️

💈範例

• replit：var redeclaration

function f() {
    
    var a = 123;        // var declaration
    
    var a = 'hello';    // ⭐️ var redeclaration 
                        //    • "declaration": ignored.
                        //    • "assignment" : applied❗
    
    log(a);             // 'hello'
}

📘 手冊

• Statements and declarations ⟩ declaring variables ⟩ var