Mastering JavaScript Fundamentals for a Stronger Career

Hi guys… today we’re clearing up a very common misunderstanding — “JavaScript has no types” — and then gently building up to how TypeScript makes those types visible, safer, and easier to work with. Simple ideas, real examples. 😊✨ 🌟 1. Vanilla JavaScript has types too! 🎯 JavaScript is dynamically typed, not untyped. That means: types exist but they are checked at runtime, not while coding Example: let count = 10; // number count = "ten"; // now string JavaScript allows this. It trusts the developer. 👉 The problem isn’t types don’t exist — it’s that JavaScript doesn’t warn you early. 🌟 2. Type inference vs type assignment 🧠 Type Inference TypeScript automatically figures out the type. let total = 100; // inferred as number // total = "100"; // ❌ error You didn’t tell TypeScript the type. It inferred it. Type Assignment You explicitly define the type. let total: number = 100; 👉 Use inference when code is obvious. 👉 Use assignment when clarity matters. 🌟 3. Assigning types to function parameters ⚙️ This is where TypeScript shines. JavaScript: function greet(name) { return "Hello " + name; } TypeScript: function greet(name: string): string { return "Hello " + name; } Now: you know what goes in you know what comes out wrong usage is blocked early greet(10); // ❌ error 🌟 4. The any type — power with risk ⚠️ any means: “I don’t care about the type.” let value: any = "hello"; value = 10; value = true; It turns off type checking. 👉 Useful for: ✔ quick prototypes ✔ legacy JavaScript migration 👉 Dangerous because: ❌ no safety ❌ runtime bugs return Rule of thumb: Use any only when you have no better option. 🌟 5. Union types — one value, multiple allowed types 🔀 Union types allow more than one type. let id: number | string; id = 101; id = "A101"; Very common in real apps: API responses optional values user input 👉 This is controlled flexibility — not chaos. 🌟 6. Arrays & types 📦 Arrays can be strongly typed. let marks: number[] = [80, 90, 85]; Only numbers allowed: marks.push(95); // ✅ marks.push("A"); // ❌ Array of strings: let names: string[] = ["Lakshmi", "Anu"]; Array with union types: let values: (number | string)[] = [1, "two", 3]; 🌟 7. Why all this matters 🌱 These features: ✔ reduce runtime errors ✔ make code self-explanatory ✔ improve autocomplete ✔ build confidence while changing code You’re not writing more code. You’re writing clearer code. 🌼 JavaScript already has types — TypeScript just turns the lights on. Inference keeps code clean. Explicit types keep teams safe. And together, they help code grow without breaking. ✨ #Topic3 #TypeScript ##LearnTypeScriptIn10Days

In a Javascript L1 & L2 round the following questions can be asked from interviewer. 1. What is the difference between 'Pass by Value' and 'Pass by Reference'? 2. What is the difference between map and filter ? 3. What is the difference between map() and forEach() 4. What is the difference between Pure and Impure functions? 5. What is the difference between for-in and for-of ? 6. What are the differences between call(), apply() and bind() ? 7. List out some key features of ES6 ? 8. What’s the spread operator in javascript ? 9. What is rest operator in javascript ? 10. What are DRY, KISS, YAGNI, SOLID Principles ? 11. What is temporal dead zone ? 12. Different ways to create object in javascript ? 13. Whats the difference between Object.keys,values and entries 14. Whats the difference between Object.freeze() vs Object.seal() 15. What is a polyfill in javascript ? 16. What is generator function in javascript ? 17. What is prototype in javascript ? 18. What is IIFE ? 19. What is CORS ? 20. What are the different datatypes in javascript ? 21. What are the difference between typescript and javascript ? 22. What is authentication vs authorization ? 23. Difference between null and undefined ? 24. What is the output of 3+2+”7” ? 25. Slice vs Splice in javascript ? 26. What is destructuring ? 27. What is setTimeOut in javascript ? 28. What is setInterval in javascript ? 29. What are Promises in javascript ? 30. What is a callstack in javascript ? 31. What is a closure ? 32. What are callbacks in javascript ? 33. What are Higher Order Functions in javascript ? 34. What is the difference between == and === in javascript ? 35. Is javascript a dynamically typed language or a statically typed language 36. What is the difference between Indexeddb and sessionstorage ? 37. What are Interceptors ? 38. What is Hoisting ? 39. What are the differences let, var and const ? 41. Differences between Promise.all, allSettled, any, race ? 42. What are limitations of arrow functions? 43. What is difference between find vs findIndex ? 44. What is tree shaking in javascrip 45. What is the main difference between Local Storage and Session storage 46. What is eval() 47. What is the difference between Shallow copy and deep copy 48. What are the difference between undeclared and undefined variables 49. What is event bubbling 50. What is event capturing 51. What are cookies 52. typeOf operator 53. What is this in javascript and How it behaves in various scenarios 54. How do you optimize the performance of application 55. What is meant by debouncing and throttling

In a Javascript L1 & L2 round the following questions can be asked from interviewer. 1. What is the difference between 'Pass by Value' and 'Pass by Reference'? 2. What is the difference between map and filter ? 3. What is the difference between map() and forEach() 4. What is the difference between Pure and Impure functions? 5. What is the difference between for-in and for-of ? 6. What are the differences between call(), apply() and bind() ? 7. List out some key features of ES6 ? 8. What’s the spread operator in javascript ? 9. What is rest operator in javascript ? 10. What are DRY, KISS, YAGNI, SOLID Principles ? 11. What is temporal dead zone ? 12. Different ways to create object in javascript ? 13. Whats the difference between Object.keys,values and entries 14. Whats the difference between Object.freeze() vs Object.seal() 15. What is a polyfill in javascript ? 16. What is generator function in javascript ? 17. What is prototype in javascript ? 18. What is IIFE ? 19. What is CORS ? 20. What are the different datatypes in javascript ? 21. What are the difference between typescript and javascript ? 22. What is authentication vs authorization ? 23. Difference between null and undefined ? 24. What is the output of 3+2+”7” ? 25. Slice vs Splice in javascript ? 26. What is destructuring ? 27. What is setTimeOut in javascript ? 28. What is setInterval in javascript ? 29. What are Promises in javascript ? 30. What is a callstack in javascript ? 31. What is a closure ? 32. What are callbacks in javascript ? 33. What are Higher Order Functions in javascript ? 34. What is the difference between == and === in javascript ? 35. Is javascript a dynamically typed language or a statically typed language 36. What is the difference between Indexeddb and sessionstorage ? 37. What are Interceptors ? 38. What is Hoisting ? 39. What are the differences let, var and const ? 41. Differences between Promise.all, allSettled, any, race ? 42. What are limitations of arrow functions? 43. What is difference between find vs findIndex ? 44. What is tree shaking in javascrip 45. What is the main difference between Local Storage and Session storage 46. What is eval() 47. What is the difference between Shallow copy and deep copy 48. What are the difference between undeclared and undefined variables 49. What is event bubbling 50. What is event capturing 51. What are cookies 52. typeOf operator 53. What is this in javascript and How it behaves in various scenarios 54. How do you optimize the performance of application 55. What is meant by debouncing and throttling.

In a Javascript L1 & L2 round the following questions can be asked from interviewer. 1. What is the difference between 'Pass by Value' and 'Pass by Reference'? 2. What is the difference between map and filter ? 3. What is the difference between map() and forEach() 4. What is the difference between Pure and Impure functions? 5. What is the difference between for-in and for-of ? 6. What are the differences between call(), apply() and bind() ? 7. List out some key features of ES6 ? 8. What’s the spread operator in javascript ? 9. What is rest operator in javascript ? 10. What are DRY, KISS, YAGNI, SOLID Principles ? 11. What is temporal dead zone ? 12. Different ways to create object in javascript ? 13. Whats the difference between Object.keys,values and entries 14. Whats the difference between Object.freeze() vs Object.seal() 15. What is a polyfill in javascript ? 16. What is generator function in javascript ? 17. What is prototype in javascript ? 18. What is IIFE ? 19. What is CORS ? 20. What are the different datatypes in javascript ? 21. What are the difference between typescript and javascript ? 22. What is authentication vs authorization ? 23. Difference between null and undefined ? 24. What is the output of 3+2+”7” ? 25. Slice vs Splice in javascript ? 26. What is destructuring ? 27. What is setTimeOut in javascript ? 28. What is setInterval in javascript ? 29. What are Promises in javascript ? 30. What is a callstack in javascript ? 31. What is a closure ? 32. What are callbacks in javascript ? 33. What are Higher Order Functions in javascript ? 34. What is the difference between == and === in javascript ? 35. Is javascript a dynamically typed language or a statically typed language 36. What is the difference between Indexeddb and sessionstorage ? 37. What are Interceptors ? 38. What is Hoisting ? 39. What are the differences let, var and const ? 41. Differences between Promise.all, allSettled, any, race ? 42. What are limitations of arrow functions? 43. What is difference between find vs findIndex ? 44. What is tree shaking in javascrip 45. What is the main difference between Local Storage and Session storage 46. What is eval() 47. What is the difference between Shallow copy and deep copy 48. What are the difference between undeclared and undefined variables 49. What is event bubbling 50. What is event capturing 51. What are cookies 52. typeOf operator 53. What is this in javascript and How it behaves in various scenarios 54. How do you optimize the performance of application 55. What is meant by debouncing and throttling #js #javascript #react #next #v8

In a Javascript L1 & L2 round the following questions can be asked from interviewer. 1. What is the difference between 'Pass by Value' and 'Pass by Reference'? 2. What is the difference between map and filter ? 3. What is the difference between map() and forEach() 4. What is the difference between Pure and Impure functions? 5. What is the difference between for-in and for-of ? 6. What are the differences between call(), apply() and bind() ? 7. List out some key features of ES6 ? 8. What’s the spread operator in javascript ? 9. What is rest operator in javascript ? 10. What are DRY, KISS, YAGNI, SOLID Principles ? 11. What is temporal dead zone ? 12. Different ways to create object in javascript ? 13. Whats the difference between Object.keys,values and entries 14. Whats the difference between Object.freeze() vs Object.seal() 15. What is a polyfill in javascript ? 16. What is generator function in javascript ? 17. What is prototype in javascript ? 18. What is IIFE ? 19. What is CORS ? 20. What are the different datatypes in javascript ? 21. What are the difference between typescript and javascript ? 22. What is authentication vs authorization ? 23. Difference between null and undefined ? 24. What is the output of 3+2+”7” ? 25. Slice vs Splice in javascript ? 26. What is destructuring ? 27. What is setTimeOut in javascript ? 28. What is setInterval in javascript ? 29. What are Promises in javascript ? 30. What is a callstack in javascript ? 31. What is a closure ? 32. What are callbacks in javascript ? 33. What are Higher Order Functions in javascript ? 34. What is the difference between == and === in javascript ? 35. Is javascript a dynamically typed language or a statically typed language 36. What is the difference between Indexeddb and sessionstorage ? 37. What are Interceptors ? 38. What is Hoisting ? 39. What are the differences let, var and const ? 41. Differences between Promise.all, allSettled, any, race ? 42. What are limitations of arrow functions? 43. What is difference between find vs findIndex ? 44. What is tree shaking in javascrip 45. What is the main difference between Local Storage and Session storage 46. What is eval() 47. What is the difference between Shallow copy and deep copy 48. What are the difference between undeclared and undefined variables 49. What is event bubbling 50. What is event capturing 51. What are cookies 52. typeOf operator 53. What is this in javascript and How it behaves in various scenarios 54. How do you optimize the performance of application 55. What is meant by debouncing and throttling 𝐠𝐞𝐭 𝐞𝐛𝐨𝐨𝐤 𝐰𝐢𝐭𝐡 (detailed 232 ques = 90+ frequently asked Javascript interview questions and answers, 90+ Reactjs Frequent Ques & Answers, 50+ Output based ques & ans, 23+ Coding Questions & ans, 2 Machine coding ques & ans) 𝐄𝐛𝐨𝐨𝐤 𝐋𝐢𝐧𝐤: https://lnkd.in/gJMmH-PF Follow on Instagram : https://lnkd.in/gXTrcaKP #javascriptdeveloper #reactjs #reactnative #vuejsdeveloper #angular #angulardeveloper

In a Javascript L1 & L2 round the following questions can be asked from interviewer. 1. What is the difference between 'Pass by Value' and 'Pass by Reference'? 2. What is the difference between map and filter ? 3. What is the difference between map() and forEach() 4. What is the difference between Pure and Impure functions? 5. What is the difference between for-in and for-of ? 6. What are the differences between call(), apply() and bind() ? 7. List out some key features of ES6 ? 8. What’s the spread operator in javascript ? 9. What is rest operator in javascript ? 10. What are DRY, KISS, YAGNI, SOLID Principles ? 11. What is temporal dead zone ? 12. Different ways to create object in javascript ? 13. Whats the difference between Object.keys,values and entries 14. Whats the difference between Object.freeze() vs Object.seal() 15. What is a polyfill in javascript ? 16. What is generator function in javascript ? 17. What is prototype in javascript ? 18. What is IIFE ? 19. What is CORS ? 20. What are the different datatypes in javascript ? 21. What are the difference between typescript and javascript ? 22. What is authentication vs authorization ? 23. Difference between null and undefined ? 24. What is the output of 3+2+”7” ? 25. Slice vs Splice in javascript ? 26. What is destructuring ? 27. What is setTimeOut in javascript ? 28. What is setInterval in javascript ? 29. What are Promises in javascript ? 30. What is a callstack in javascript ? 31. What is a closure ? 32. What are callbacks in javascript ? 33. What are Higher Order Functions in javascript ? 34. What is the difference between == and === in javascript ? 35. Is javascript a dynamically typed language or a statically typed language 36. What is the difference between Indexeddb and sessionstorage ? 37. What are Interceptors ? 38. What is Hoisting ? 39. What are the differences let, var and const ? 41. Differences between Promise.all, allSettled, any, race ? 42. What are limitations of arrow functions? 43. What is difference between find vs findIndex ? 44. What is tree shaking in javascrip 45. What is the main difference between Local Storage and Session storage 46. What is eval() 47. What is the difference between Shallow copy and deep copy 48. What are the difference between undeclared and undefined variables 49. What is event bubbling 50. What is event capturing 51. What are cookies 52. typeOf operator 53. What is this in javascript and How it behaves in various scenarios 54. How do you optimize the performance of application 55. What is meant by debouncing and throttling 𝐠𝐞𝐭 𝐞𝐛𝐨𝐨𝐤 𝐰𝐢𝐭𝐡 (detailed 232 ques = 90+ frequently asked Javascript interview questions and answers, 90+ Reactjs Frequent Ques & Answers, 50+ Output based ques & ans, 23+ Coding Questions & ans, 2 Machine coding ques & ans) 𝐄𝐛𝐨𝐨𝐤 𝐋𝐢𝐧𝐤: https://lnkd.in/gJMmH-PF Follow on Instagram : https://lnkd.in/gXTrcaKP #javascriptdeveloper #reactjs #reactnative #vuejsdeveloper #angular #angulardeveloper

💛 JavaScript Functions (Part 1) — What They Are & How They Work 🧠 In JavaScript, functions are not just blocks of code. They are first-class citizens, execution units, and one of the most powerful and beautiful features of the language. Let’s start from the foundation 👇 ♦️ What is a Function? A function is: 👉 A reusable block of code designed to perform a specific task. In simple words: Write once, use many times. function greet() { console.log("Hello, JavaScript!"); } ♦️ Why Functions Exist? Functions help you: ✅ Avoid code repetition ✅ Improve readability ✅ Break big problems into smaller pieces ✅ Organize logic clearly ♦️ Function Syntax (Basic) function functionName(parameters) { // function body return value; } ♦️ Parameters vs Arguments (Very Important ⚠️) 🔹 Parameters ▪️Variables listed in function definition ▪️Act like placeholders function square(num) { return num * num; } Here, num is a parameter 🔹 Arguments ▪️Actual values passed when calling a function ▪️square(5); Here, 5 is an argument 📌 Rule: Parameters receive values, arguments send values. ♦️ Calling / Invoking a Function 📞 A function does nothing until it is called. greet(); // function call square(4); // function invocation 👉 Parentheses () trigger execution. ♦️ How Functions Work Internally in JavaScript 🧠⚙️ When a function is invoked: 1️⃣ A new Function Execution Context is created 2️⃣ Memory is allocated for: Parameters and Local variables 3️⃣ Code inside the function executes line by line 4️⃣ Function returns a value (or undefined) 5️⃣ Execution context is removed from the Call Stack ♦️ Execution Flow Example var x = 10; function add(a, b) { var sum = a + b; return sum; } var result = add(2, 3); console.log(result); 🔍 Behind the Scenes Global Execution Context is created add() is called → new Function Execution Context a = 2, b = 3, sum = 5 return sum → execution context destroyed result = 5 ♦️ Functions Always Return Something function test() {} console.log(test()); // undefined 👉 If no return, JavaScript returns undefined by default. 🧠 Key Takeaways ▪️Functions are reusable blocks of logic ▪️Parameters ≠ Arguments ▪️Functions create their own execution context ▪️Function calls are managed by the call stack 📌 This was Part 1 — the foundation. Next parts coming up 🔥 👉 Part 2: Function Expressions, Arrow Functions & First-Class Functions 👉 Part 3: Higher-Order Functions, Callbacks with EventListener If this helped you, drop a 💛 or share 🔁 Learning JavaScript deeply, one concept at a time 🚀 #JavaScript #JSInternals #LearnJavaScript #WebDevelopment  #ProgrammingConcepts #WebDevJourney #BuildInPublic

⚡ JavaScript Concepts JavaScript powers interactive experiences, from dynamic updates to full apps. Start with variables: use let for changeable values, const for fixed ones, and var (older style) sparingly. For instance, let score = 0; score++; updates a game score on the fly. Functions are reusable code blocks. Declare them with function add(a, b) { return a + b; } or arrow syntax: const add = (a, b) => a + b;. They handle tasks like validating forms without repeating code. Core JavaScript Concepts Variables and Data Types JavaScript uses dynamic typing. Declare with let, const, or var. Primitives include strings ("hello"), numbers (42), booleans (true), null, undefined, and symbols. Objects and arrays store collections: const arr = [1, 'two', {key: 'value'}];. Functions and Scope Functions encapsulate logic. Example: javascript function greet(name) { return `Hello, ${name}!`; } console.log(greet('World')); // Hello, World! Scope limits variable access—block scope with let/const keeps things tidy. Control Structures Use if/else for decisions, for/while loops for repetition, and switch for multiple cases. javascript for (let i = 0; i < 3; i++) { console.log(i); // 0, 1, 2 } Arrays and Objects Arrays: push(), pop(), map(), filter(). Objects: key-value pairs with dot/bracket notation. Destructuring shines: const {name, age} = user;. DOM Manipulation Access HTML with document.getElementById('id'). Add events: button.addEventListener('click', () => alert('Clicked!'));. ES6+ Features Arrow Functions: Concise callbacks. Promises/Async-Await: Handle async code like fetches. javascript async function fetchData() { const data = await fetch('api/url'); return data.json(); } Modules: export/import for modular code. Practice these in the browser console to build intuition—they form the backbone of modern JS. #JavaScript #JSConcepts #Development #CodingTips #Programming #Skills #JSBook #JavaScriptTutorial #Frontend #ES6 #DOM #Backend #DataStructure

I have a confession to make. I am not very savvy in JavaScript, its syntax, or structure. Everything I've learned about writing JavaScript I learned from borrowing code from sections of this 15+ year old in-house application. Making things fast has always fallen under the shadow of making things right. Software that is "good enough" wins almost every time, but is "good enough" really good enough?   I'm no dummy. My co-workers have provided a few tools and processes to recognize how to locate, 'copy what works', and modify it as needed. This has been successful, but doing so always left me feeling empty and unsure. It was frustrating to know something worked, passed testing, and provided value. As they say, "when all you have is a hammer, everything looks like nails". The daunting task of writing scripts to process front-end UI forms has always been a mystery. This is why I've stuck to the back-end of our application when given the chance.   Lately I have been "hitting the books" to better understand how to use JavaScript, what Node.js is, and how AJAX does its job to communicate with the back-end. For example, I have learned that there are two ways to create a JavaScript object; with "object literal notation" or constructor notation. I have also learned there are a million ways to mangle a JS object after the object is created (not cool). Why am I hitting the books when I've glided by for so many years by copy-paste-test? What is so special about JavaScript when there are so many other languages available? Who, in the 21st century, doesn't know how to use jQuery? These are a lot of good questions. First, I want to do a better job at my... job. I'm not lazy. There is so much to do every day. I could continue doing what I'm doing and probably never run into any trouble. So, to answer the first question, hitting the books allows me to exercise this meat on a stick called a "brain". By understanding the language, I can contribute by fixing a lot of the issues I was propagating because now I can recognize how fragile JS is. Second, why JavaScript? Because it pays my bills. It is a viable language to this day. It doesn't seem to be slowing down, and there are more and more languages that borrow from its syntax. I don't think it is a losing proposition to learn as much as I can about JavaScript. Lastly, who doesn't know jQuery? Well, me for one. There is a lot to learn about it. It is apparent that developers only use a handful of the language's built-in functions. For example, the AJAX jQuery methods are super useful. However, most of the jQuery AJAX methods such as .get(), .post(), .getJSON() are overlooked in lieu of the call to .ajax(). This leads to many more lines of code and doesn't' self-document. There's my confession. I'm not willing to keep walking the same path forward. I enjoy what I do and I want to be better at it every day.

Hoisting in JavaScript: The Truth Behind undefined, TDZ & ReferenceError If you’re learning JavaScript, this confusion is almost guaranteed 👇 console.log(a); // undefined var a = 10; But… console.log(b); // ReferenceError let b = 20; Same idea, different result 🤯 So what’s really happening? Let’s break it down step by step:- 🔹 What JavaScript Does Before Running Your Code Before execution starts, JavaScript goes through a memory creation phase. In this phase: Variable and function names are registered in memory This behavior is called hoisting Nothing is executed yet — JavaScript is just preparing. 🔹 Why var Gives undefined When JavaScript sees: var x = 5; During the memory phase: x is created in memory Its value is set to undefined If x is accessed before assignment, JavaScript knows it exists but its value is undefined. After the execution phase assigns x = 5, console.log(x) correctly prints 5. That’s why no error, only undefined. 🔹 Now the Important Part: let, const & TDZ Yes - let and const are also hoisted. This surprises many people. But here’s the key difference 👇 They are hoisted into a special time window called: ⏳ Temporal Dead Zone (TDZ) 🔹 What is Temporal Dead Zone (TDZ)? TDZ is the time period: From the start of the block until the line where the variable is declared During this time: The variable exists in memory but accessing it is strictly not allowed Example: console.log(y); // ReferenceError let y = 10; JavaScript knows y exists, but says ❌ You’re accessing it too early. Hence, ReferenceError. 🔹 Why JavaScript Designed It This Way TDZ exists to: Prevent bugs caused by accidental early access Force cleaner, predictable code Make developers think before using variables This is why let and const are safer than var. 🔹 Function Hoisting hello(); // Works function hello() { console.log("Hello!"); } Function declarations are fully available during the memory phase, so they can be called even before they are written. 🎯 Final Thought Hoisting is not magic. It’s just how JavaScript prepares your code before execution. Once you understand: Memory phase Execution phase And TDZ Hoisting stops being confusing 😊 💬 Have you ever been stuck with undefined or ReferenceError because of hoisting? Drop a comment - let’s learn together #JavaScript #Hoisting #TDZ #LearningJavaScript #DeveloperMindset