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🈯const

JS ⟩ variable ⟩ const
JS ⟩ declaration ⟩ variable ⟩ const

⭐️ ES6 (2015)

(declaration) declares a local constant in block scope.

const

must have an initial value❗ (👉 more)
can't be reassigned❗ (👉 )
can't be ❗

⛔ ReferenceError: .

caused by referencing a / / in its ❗

✅ it's common to declare const using capital letters.

using on (/ / ) in its will throw a .

replit：

Previousvar can shadow parameter even in strict mode❗️Nextconst requires initialization

Last updated 2 years ago

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// ⭐ temporal dead zone (start)
// ------------------------------
typeof aLet;       // ⛔ ReferenceError: Cannot access 'aLet' before initialization
typeof aConst;     // ⛔ ReferenceError: Cannot access 'aConst' before initialization
typeof aClass;     // ⛔ ReferenceError: Cannot access 'aClass' before initialization

typeof undeclared;        // ❗ 'undefined'

// ⭐ lexical declarations (let/const/class)
// --------------------------------------------
let aLet;                 // ⭐ initialized to `undefined`
const aConst = "hello";
class aClass {}