Global Scope vs Block Scope in JavaScript

Understanding scope is fundamental in JavaScript. It determines where variables are accessible.

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🌍 Global Scope

• Variables declared outside any block or function.
• Accessible anywhere in the code.

Example:

var name = "Nutan";

function greet() {
  console.log("Hello", name);
}

greet(); // Hello Nutan

✅ name is globally accessible.

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📦 Block Scope

• Introduced with let and const.
• Limited to the block {} where it's defined.

Example:

{
  let age = 25;
  console.log(age); // 25
}
console.log(age); // ❌ ReferenceError: age is not defined

Variables defined with let or const inside {} are not accessible outside.

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⚠️ var Does NOT Respect Block Scope

{
  var city = "Delhi";
}
console.log(city); // ✅ Delhi

❌ var is function-scoped, not block-scoped.

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🔍 Comparison Table

Scope Type	Keyword(s)	Accessible From	Use Case
Global Scope	var, let, const	Anywhere after declaration	App-wide constants, functions
Block Scope	let, const	Inside {} only	Loops, conditionals, functions

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✅ Best Practices

• Prefer let and const for block scope safety.
• Avoid polluting the global scope.