JavaScript: undefined vs not defined explained

👉✅ “Setting a one-week goal to revise JavaScript again.” 💻Topic-1. JavaScript Constructor Function Hey everyone, 👋 Today, let’s talk about an interesting JavaScript topic — the Constructor Function. This is a special type of function that helps us create multiple similar objects without writing the same code again and again! 🔁 🧠 Key points to understand: The name of a constructor function always starts with a capital letter. We use the new keyword when creating an object. It automatically returns a new object. Through this concept, we can explore the basics of Object-Oriented Programming (OOP) in JavaScript — including concepts like inheritance and encapsulation. 🚀 If you’re learning JavaScript, understanding constructor functions is a must-have skill — it makes your code cleaner, reusable, and more efficient! #JavaScript #WebDevelopment #CodingTips #ConstructorFunction #FrontendDevelopment #LearningEveryday

💡 JavaScript Trivia: Did you know that in JavaScript, the expression NaN === NaN actually returns false? 🤯 That’s because NaN (Not-a-Number) is special — it’s not equal to anything, not even itself. This behavior follows the IEEE 754 standard for floating-point numbers. So if NaN isn’t equal to itself, how do we check for it? That’s where isNaN() and Number.isNaN() come in. The older isNaN() function tries to convert the value into a number before checking, which can give confusing results — for example, isNaN('hello') returns true because the string can’t be turned into a number. The newer Number.isNaN() is smarter and stricter: it only returns true when the value is literally NaN, not just something that can’t be converted to a number. ✅ Best practice: use Number.isNaN() whenever possible — it’s more predictable and avoids type coercion headaches. A tiny quirk, but one that’s tripped up many JavaScript devs (including me at some point 😅). #JavaScript #WebDevelopment #CodingTips #Programming #Trivia #Fact

How JS Converts [] + {} to [object Object] —🤯 JavaScript can be weirdly magical sometimes. Ever tried this in your console? 👇 [] + {} // Output: "[object Object]" At first glance, it looks confusing — why does an empty array and an empty object become a string? Let’s decode the magic 🪄 1️⃣ + Operator in JS The + operator doesn’t just add numbers — it can also concatenate strings. 2️⃣ Type Conversion Happens! [] (empty array) → when converted to string becomes "" (empty string). {} (empty object) → when converted to string becomes "[object Object]". 3️⃣ Final Expression So JS actually does: "" + "[object Object]" → "[object Object]" ✅ Bonus twist: Try reversing it: {} + [] Now it gives 0 because {} is treated as an empty block,not an object. 🤯 JavaScript — where logic meets magic ✨ 🔹 Follow Prashansa Sinha for more fun JS mysteries and simple explanations 👩💻 #JavaScript #WebDevelopment #Coding #Frontend #JS #LearnToCode #Programming #TechCommunity #Developers #CodeNewbie #WebDev

⚡ 𝐉𝐚𝐯𝐚𝐒𝐜𝐫𝐢𝐩𝐭 𝐇𝐨𝐢𝐬𝐭𝐢𝐧𝐠 𝐚𝐧𝐝 𝐒𝐜𝐨𝐩𝐞 𝐌𝐚𝐝𝐞 𝐒𝐢𝐦𝐩𝐥𝐞 ⚡ In JavaScript, two important concepts — 𝐡𝐨𝐢𝐬𝐭𝐢𝐧𝐠 and 𝐬𝐜𝐨𝐩𝐞 — control how your code runs. 𝐇𝐨𝐢𝐬𝐭𝐢𝐧𝐠 means JavaScript moves all variable and function declarations to the top before the code runs. That’s why you can sometimes use a function before it’s written. But remember — only declarations are hoisted, not values! Variables declared with var become undefined, while let and const are not accessible before declaration. 𝐒𝐜𝐨𝐩𝐞 decides where your variables can be used. 🌍 𝐆𝐥𝐨𝐛𝐚𝐥 Scope – You can use the variable anywhere in the program. ⚙️ 𝐅𝐮𝐧𝐜𝐭𝐢𝐨𝐧 Scope – The variable works only inside that function. 📦 𝐁𝐥𝐨𝐜𝐤 Scope – Works only inside { }, when declared with let or const. Understanding hoisting and scope helps you know how JavaScript actually reads and runs your code — and that’s the key to avoiding errors and writing better programs. #javascript #js #Hoisting #Scope #softwaredeveloper #JavaScriptTips #JSTutorial #webdevelopment #frontenddevelopment #CodingTips #JavaScriptDeveloper #ES6 #Programming #Coding #JSLearning #JSTypes #education #LearnJavaScript #technology #w3schools #careers

Today, I explored an important JavaScript concept Hoisting. Hoisting means JavaScript moves declarations (not initializations) to the top of their scope before code execution.

💡 Understanding Object Methods in JavaScript Working with objects is fundamental in JS. Here's a quick overview of some powerful methods: Object.keys(obj) → Returns all keys of the object. Object.values(obj) → Returns all values of the object. Object.entries(obj) → Returns key-value pairs as arrays. obj.hasOwnProperty("property") → Checks if the object has a specific property. Object.assign({}, obj, { newProperty: "newValue" }) → Creates a new object by merging existing ones. 👉 View the full example on GitHub: https://lnkd.in/dDN-vDkD #JavaScript #FullStack #100xDevs #WebDevelopment #Coding #JSConcepts #LearnJavaScript

🔒 JavaScript Closures: The Private Diary Analogy Ever wondered how JavaScript "remembers" things? Let me explain closures with a real-world analogy. Think of a closure like a private diary with a lock: 📖 The diary (outer function) contains your secrets (variables) 🔐 Only you have the key (inner function) to access those secrets ✨ Even after you close the diary, the key still works Why does this matter? The count variable is trapped inside the closure. No one can directly access or modify it from outside. It's like data privacy built into JavaScript! Real-world use case : This powers every search bar you've used that waits for you to stop typing! The key insight: Closures let inner functions remember their environment, even after the outer function has finished executing. Have you used closures in your code today? Share your favorite use case below! 👇 #JavaScript #WebDevelopment #ReactJS #Programming #Frontend #CodingTips #SoftwareEngineering

Prototypes JavaScript is an object-oriented language built around a prototype model. In JavaScript, every object inherits properties from its prototype, if there are any. A prototype is simply an object from which another object inherits properties. To create complex programs using JavaScript, one has to be proficient in working with prototypes — they form the very core of OOP in the language.

Did you know this about JavaScript? In JavaScript: [ ] == ![ ] is true. Wait, what? Here’s why: ![ ] becomes false because an empty array is truthy. So the expression becomes [ ] == false. JavaScript tries to convert both sides to the same type. Number([ ]) is 0, and Number(false) is also 0. Therefore, 0 == 0 → true. This is one of the reasons developers say: "JavaScript is simple… until it isn’t." I’m currently learning JavaScript and finding these little quirks really fascinating. If you’re also learning, what’s the weirdest or most surprising thing you’ve discovered so far? #JavaScript #WebDevelopment #CodingJourney #100DaysOfCode #DidYouKnow #LearnInPublic #FrontendDevelopment

Accidentally Discovered Something Cool in JavaScript! 😎 While working on some JavaScript code, I accidentally came across the ! and !! operators - and it turned out to be a really interesting find 😄 At first, I was confused 🤔 but after a bit of testing, it all made sense! - The ! (NOT) operator converts true -> false, and vice versa. - The !! (Double NOT) operator converts any value into its boolean equivalent value and its great for checking if something is truthy or falsy. This tiny trick makes conditions cleaner and helps when validating inputs or checking existence of values in JavaScript. Tiny discoveries like these remind me how fun it is to explore and learn JavaScript every day! 😊 . . . . . . . #WebDevelopment #JavaScript #Frontend #CodingJourney #LearningByDoing #Developer #Coding #LearningToCode #FrontendDevelopment #DevelopersCommunity #CodingTips #CodeWithMe #CleanCode #CodeBetter #DevLife