JavaScript Interview Preparation Notes

This repository contains comprehensive notes and examples for JavaScript interview preparation, covering key concepts and common interview questions.

Project Structure

interview_questions/
├── variableShadowing.js    # Examples of variable shadowing
├── higherOrderFunction.js  # Higher order functions and callbacks
├── pureFunction.js         # Pure vs impure functions
└── thiskeyword.js         # Understanding 'this' keyword

Topics Covered

1. Variable Shadowing

• Definition: When a variable in a lower scope has the same name as a variable in a higher scope
• Examples showing different scopes (global, function, block)
• Best practices and common pitfalls

2. Higher Order Functions

• Functions that take other functions as arguments
• Functions that return other functions
• Callback functions
• Common use cases and examples

3. Pure Functions

• Characteristics of pure functions
• Side effects and their impact
• Examples of pure vs impure functions
• Advantages and disadvantages

4. this Keyword

• Different contexts of 'this'
• Regular functions vs arrow functions
• Constructor functions
• Event handlers
• call(), apply(), and bind()

How to Use

1. Clone the repository
2. Navigate to the interview_questions directory
3. Open any .js file to view examples and explanations
4. Run the examples using Node.js or in browser console

Running Examples

# Using Node.js
node interview_questions/variableShadowing.js
node interview_questions/higherOrderFunction.js
node interview_questions/pureFunction.js
node interview_questions/thiskeyword.js

Key Concepts

Variable Shadowing

let x = 10; // Global scope

function myFunction() {
    let x = 20; // Function scope
    console.log(x); // 20
}

Higher Order Functions

function greet(name, callback) {
    console.log(`Hello, ${name}!`);
    callback();
}

Pure Functions

// Pure
function add(a, b) {
    return a + b;
}

// Impure
let counter = 0;
function increment() {
    counter++;
    return counter;
}

this Keyword

const person = {
    name: "John",
    greet: function() {
        console.log(`Hello, ${this.name}`);
    }
};

Interview Tips

1. Variable Shadowing

   • Understand scope hierarchy
   • Be aware of naming conflicts
   • Know when shadowing might cause issues

2. Higher Order Functions

   • Explain the concept clearly
   • Provide real-world examples
   • Understand callback patterns

3. Pure Functions

   • Explain side effects
   • Discuss benefits and trade-offs
   • Provide practical examples

4. this Keyword

   • Know different contexts
   • Understand arrow functions
   • Be familiar with binding methods

Additional Resources

• MDN Web Docs
• JavaScript.info
• Eloquent JavaScript

Contributing

Feel free to contribute by:

1. Adding more examples
2. Improving explanations
3. Adding new topics
4. Fixing any errors

License

This project is open source and available under the MIT License.