❗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❗)

JS is lenient with var, strict with let.

var redeclaration applied even in strict mode❗️
let redeclaration not allowed even in sloppy mode❗️

replit：var redeclaration

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

Previousglobal var / function is global object property❗️Nextvar in block can't shadow outer let❗️

Last updated 3 years ago

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