JavaScript, Function vs Block Scope

Explain Function Scope vs Block Scope in JavaScript by some examples.
Answer: In JavaScript, scope refers to the accessibility of variables, functions, and objects in some particular part of your code during runtime. There are mainly two types of scopes you'll often deal with: function scope and block scope.Function scope means that variables defined within a function are only accessible within that function. This is how JavaScript has traditionally scoped variables using the 'var' keyword.
Example:
function myFunction() {
var functionScopedVariable = "I'm only accessible within this function";
console.log(functionScopedVariable); // This works
}
myFunction();
console.log(functionScopedVariable); // Error: functionScopedVariable is not defined

In this example, 'functionScopedVariable' is only accessible inside 'myFunction'. Attempting to access it outside the function results in an error.Block scope refers to variables that are accessible only within the block (denoted by '{}') where they are defined. Block scope is introduced with the 'let' and 'const' keywords in ES6 (ECMAScript 2015).
Example with 'let':
if (true) {
let blockScopedVariable = "I'm only accessible within this block";
console.log(blockScopedVariable); // This works
}
console.log(blockScopedVariable); // Error: blockScopedVariable is not defined

In this example, 'blockScopedVariable' is only accessible within the 'if' block. Attempting to access it outside the block results in an error.
Example with 'const':
if (true) {
const anotherBlockScopedVariable = "I'm also only accessible within this block";
console.log(anotherBlockScopedVariable); // This works
}
console.log(anotherBlockScopedVariable); // Error: anotherBlockScopedVariable is not defined

Just like with 'let', 'const' variables are also block-scoped. They are confined to the block in which they are defined.Let's compare function scope and block scope with a combined example:
javascript
function testScope() {
if (true) {
var functionScoped = "I'm function scoped";
let blockScoped = "I'm block scoped";
const alsoBlockScoped = "I'm also block scoped";
}
console.log(functionScoped); // This works
console.log(blockScoped); // Error: blockScoped is not defined
console.log(alsoBlockScoped); // Error: alsoBlockScoped is not defined
}
testScope();

- 'functionScoped' is accessible within the entire 'testScope' function because it's declared with 'var' and has function scope.
- 'blockScoped' and 'alsoBlockScoped' are only accessible within the 'if' block because they are declared with 'let' and 'const', respectively, and have block scope.- Function Scope ('var'): Variables declared with 'var' are function-scoped and are accessible throughout the function in which they are declared.
- Block Scope ('let', 'const'): Variables declared with 'let' and 'const' are block-scoped and are only accessible within the block where they are defined.
Understanding these scoping rules is crucial for writing clear and bug-free JavaScript code.