Temporal Dead Zone (TDZ) and Hoisting in JavaScript:

Temporal Dead Zone (TDZ) and Hoisting in JavaScript:

1. Temporal Dead Zone (TDZ): The Temporal Dead Zone refers to the time period between entering the scope (like a block or function) and the variable being declared. In this zone, any attempt to access the variable will result in a ReferenceError. The TDZ exists for variables declared using let, const, and class before they are initialized.

Example:

console.log(myVar); // undefined
console.log(myLet); // ReferenceError: Cannot access 'myLet' before initialization

var myVar = 5;
let myLet = 10;

In the above example, myVar is declared using var, so it gets hoisted and initialized to undefined. But myLet is in the Temporal Dead Zone until its declaration, so trying to access it before the declaration throws a ReferenceError.

Key Points about TDZ:

Variables declared using let or const are not accessible before their declaration within a block scope, even though they are hoisted.

This prevents the usage of variables before they are explicitly initialized.

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1. Hoisting: Hoisting refers to the behavior in JavaScript where variable and function declarations are moved to the top of their scope (either the global scope or the function/block scope) during the compile phase. However, only the declarations are hoisted, not the initializations.

Example:

console.log(myVar); // undefined
var myVar = 5;

In the above example, the declaration of myVar is hoisted to the top, but its initialization (myVar = 5) remains at the place where it was written. So, when console.log(myVar) is called before initialization, it returns undefined.

Hoisting of var, let, const, and functions:

var: Variables declared with var are hoisted and initialized with undefined.

console.log(myVar); // undefined
var myVar = 10;

let and const: Variables declared with let and const are hoisted but are not initialized. They remain in the TDZ until their initialization.

console.log(myLet); // ReferenceError
let myLet = 20;

Function declarations: Function declarations are fully hoisted, meaning you can call the function even before the point where it's declared in the code.

myFunc(); // "Hello!"

function myFunc() {
console.log("Hello!");
}

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Key Differences Between Hoisting and TDZ:

Hoisting lifts variable and function declarations to the top of their scope.

The Temporal Dead Zone occurs for let, const, and class, where the variables are hoisted but cannot be accessed until they are initialized. This prevents accessing variables before their declaration.