#130 What is scope in Javascript? Types of scopes

Definition: Scope determines where variables are accessible in your code.

• Think of scope as the visibility or lifetime of a variable.
• Helps avoid conflicts and controls how data is shared.

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🔹 Types of Scope in JavaScript

1. Global Scope

• Variables declared outside of any function/block are in the global scope.
• Accessible everywhere in the program.

let globalVar = "I am global";

function test() {
  console.log(globalVar); // ✅ Accessible here
}

test();
console.log(globalVar); // ✅ Accessible here too

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2. Function Scope

• Variables declared inside a function are only available within that function.
• They cannot be accessed outside.

function example() {
  let localVar = "I am inside function";
  console.log(localVar); // ✅ Accessible here
}

example();
// console.log(localVar); ❌ Error: not defined

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3. Block Scope (ES6)

• Variables declared with let or const inside {} are only available inside that block.
• var does not have block scope, only function scope.

if (true) {
  let blockVar = "Inside block";
  console.log(blockVar); // ✅ Accessible here
}
// console.log(blockVar); ❌ Error

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4. Lexical Scope (Closures)

• Inner functions can access variables from their outer function (where they were created).
• This is called lexical scoping.

function outer() {
  let outerVar = "Outer variable";

  function inner() {
    console.log(outerVar); // ✅ Can access parent's variable
  }
  inner();
}

outer();

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🔹 Summary Table

Scope Type	Declared With	Accessible Where?
Global Scope	Anywhere (outside fn)	Everywhere
Function Scope	var, let, const (inside fn)	Only inside that function
Block Scope	let, const (inside {})	Only inside that block
Lexical Scope	Function inside another	Inner fn can access outer fn vars