🔮 What is Hoisting?

Hoisting is JavaScript’s default behavior of moving declarations to the top of the current scope (script or function) before the code is executed.

🧠 Think of it as:

“JavaScript scans your code for variable and function declarations before running it, and moves those declarations to the top.”

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🧪 Example 1: Variable Hoisting

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

You’d think it would throw an error, but nope — output is undefined because:

var x;        // declaration is hoisted
console.log(x); // undefined
x = 10;       // assignment stays in place

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❗ var vs let / const

console.log(y); // ❌ ReferenceError
let y = 5;

With let and const, declarations are hoisted, but not initialized. They stay in a Temporal Dead Zone (TDZ) until the line where they’re declared.

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⚙️ Example 2: Function Hoisting

greet(); // ✅ Works!
function greet() {
  console.log('Hello!');
}

👉 Entire function declarations are hoisted (both name and body).

BUT…

sayHi(); // ❌ TypeError: sayHi is not a function
var sayHi = function() {
  console.log('Hi!');
};

Because here, only the variable sayHi is hoisted (with undefined), not the function.

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📝 Summary

Feature	Hoisted?	Initialized?	Accessible Before Declaration?
var	✅ Yes	✅ Yes (with undefined)	✅ Yes (but undefined)
let / const	✅ Yes	❌ No	❌ No (TDZ error)
Function Declaration	✅ Fully	✅ Yes	✅ Yes
Function Expression (var)	✅ var only	❌ No	❌ No (TypeError)

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