Master JSON.parse and JSON.stringify in JavaScript

Debugging inconsistent runtime behavior steals time from feature delivery. ────────────────────────────── Map and Set Data Structures Guide with Examples This comprehensive guide dives deep into Map and Set data structures in JavaScript, covering their usage, architecture decisions, and advanced patterns. Learn how to leverage these powerful tools for scalability and performance in your enterprise applications. hashtag#javascript hashtag#datastructures hashtag#map hashtag#set hashtag#advanced ────────────────────────────── Core Concept The Map and Set data structures were introduced in ECMAScript 2015 (ES6) and are essential for modern JavaScript development. They provide more efficient ways to handle collections compared to traditional objects and arrays. A Map allows keys of any type, unlike regular objects that only allow strings and symbols. Internally, Maps are optimized for frequent additions and removals, making them suitable for dynamic data scenarios. On the other hand, a Set enables storage of unique values, eliminating duplicates automatically. It’s particularly useful in cases where you need to track items without repetition, such as user IDs or tags. Key Rules • Use Map for Key-Value Pairs: Opt for Maps when you need to associate keys with values. • Utilize Set for Uniqueness: Choose Sets to maintain collections of unique items. • Leverage Iterators: Use iterators for efficient traversal of both Maps and Sets. 💡 Try This // Creating a Map and a Set const map = new Map(); const set = new Set(); ❓ Quick Quiz Q: Is Map and Set Data Structures different from Object and Array? A: Yes, Map and Set differ significantly from Object and Array. While Objects only accept strings as keys, Maps can use any value. Sets automatically handle duplicates, while Arrays allow them, requiring additional logic to ensure uniqueness. 🔑 Key Takeaway In this guide, we explored the intricate workings of Map and Set data structures in JavaScript. We discussed their differences from traditional data structures, usage scenarios, and advanced patterns. Armed with this knowledge, you should be able to implement these structures effectively in your applications. ────────────────────────────── 🔗 Read the full guide with code examples & step-by-step instructions: https://lnkd.in/g2mqMWx4

Debugging inconsistent runtime behavior steals time from feature delivery. ────────────────────────────── Object.keys() values() and entries() Guide with Examples In this comprehensive guide, you'll learn how to effectively use Object.keys(), Object.values(), and Object.entries() in JavaScript. Discover their functionalities, best practices, and real-world applications with actionable examples. hashtag#javascript hashtag#object hashtag#programming hashtag#guide ────────────────────────────── Core Concept Object.keys(), Object.values(), and Object.entries() are built-in JavaScript methods introduced in ECMAScript 5. They are essential for working with objects in a more manageable way, especially as objects in JavaScript can hold a variety of data types. • Object.keys() provides an array of keys, allowing developers to access property names directly. This is useful for operations where you need to validate the presence of certain properties or when you need to transform data. • Object.values() provides an array of values, giving a straightforward way to retrieve the values associated with an object. This can be particularly helpful in scenarios where the keys are not relevant, but the values are. Key Rules • Avoid Mutating Original Objects: Use methods to create new arrays instead of directly modifying the object. • Use Destructuring for Clarity: When working with entries, destructuring can make the code clearer and more readable. • Check for Own Properties: Always ensure you're working with own properties using these methods to avoid unexpected results. 💡 Try This // Quick example of using Object.keys(), values(), and entries() const obj = { name: 'Alice', age: 25, job: 'Developer' }; console.log(Object.keys(obj)); // ['name', 'age', 'job'] ❓ Quick Quiz Q: Is Object.keys() values() and entries() different from JSON methods? A: Yes, while Object.keys(), Object.values(), and Object.entries() work directly with JavaScript objects, JSON methods like JSON.stringify() and JSON.parse() handle string representations of objects. The former are used for accessing and manipulating object properties, while the latter are for converting objects to and from string formats. 🔑 Key Takeaway In this guide, we explored the powerful methods Object.keys(), Object.values(), and Object.entries(). We discussed their usage, best practices, and provided numerous examples to illustrate their applications. As you continue to work with JavaScript, integrating these methods into your toolkit will enhance your ability to manipulate object data effectively. ────────────────────────────── 🔗 Read the full guide with code examples & step-by-step instructions: https://lnkd.in/gP4Qczbz

𝗧𝘆𝗽𝗲𝘀𝗰𝗿𝗶𝗽𝘁 𝟲.𝟬 𝗙𝗶𝘅𝗲𝘀 𝗥𝗲𝗮𝗹 𝗣𝗮𝗶𝗻 𝗣𝗼𝗶𝗻𝘁𝘀 TypeScript 6.0 solves everyday problems. It makes your code safer and your builds faster. Here is what matters for 2026. **Method syntax now works as you expect.** Before, TypeScript guessed wrong when you used a method instead of an arrow function. Now it checks if "this" is used. Both work the same. ```typescript callIt({ consume(y) { return y.toFixed(); }, // ✅ y is number now }); ``` **Clean imports with #/ prefixes are official.** Stop writing messy relative paths like "../../../utils". Use the Node.js subpath imports feature. ```typescript import * as utils from "#/utils.js"; ``` This matches bundlers like Webpack. Your imports become readable. **Your type unions will now be in a fixed order.** TypeScript 7.0 will check types in parallel. That can randomize union order like `100 | 500`. Use the new `--stableTypeOrdering` flag now to get consistent order. This keeps your compiled files clean. Note: it can slow builds by 25%. **The Temporal API has types.** Say goodbye to JavaScript Date bugs. Use the modern Temporal API for time zones and durations. ```typescript const meeting = Temporal.Instant.from("2026-04-06T10:00:00Z"); const local = meeting.toZonedDateTimeISO("America/Toronto"); ``` **Maps get two helpful new methods.** Replace manual `if (has) get() else set()` logic. ```typescript const timeout = config.getOrInsert("timeout", 5000); const value = config.getOrInsertComputed("key", () => compute()); ``` **Safely build regex from user text.** No more manual escaping bugs. Use the new built-in escape. ```typescript const safe = RegExp.escape(userInput); const regex = new RegExp(safe, "gi"); ``` **Breaking changes you must handle.** Your tsconfig.json defaults have changed. - `strict` is now true. You must list needed types. - `module` defaults to `esnext`. - `target` floats to `es2025`. - `types` defaults to an empty array. **Your migration steps:** Short-term: - Add an explicit `"types": ["node", "jest"]` array in tsconfig. - Set `"rootDir": "./src"` if your source folder is not the project root. - Remove deprecated `baseUrl` path mapping. Use full paths in `paths`. Medium-term: - Move off `target: "es5"`. Use at least ES2015. - Change `--moduleResolution node` to `nodenext` or `bundler`. - Migrate from `amd/umd/system` modules to ESM. Long-term: - Test your build with `--stableTypeOrdering`. - Plan for TypeScript 7.0's parallel checking. - Consider parallel CI builds to offset any speed changes. TypeScript 6.0 is a bridge. It cleans up old defaults and adds features for faster, more predictable future versions. The migration is clear. What feature will you try first? Source: https://lnkd.in/gu9jP4tb

✅ JavaScript Advanced Concepts You Should Know 🔍💻 These concepts separate beginner JS from production-level code. Understanding them helps with async patterns, memory, and modular apps. 1️⃣ Closures A function that "closes over" variables from its outer scope, maintaining access even after the outer function returns. Useful for data privacy and state management. function outer() { let count = 0; return function inner() { count++; console.log(count); }; } const counter = outer(); counter(); // 1 counter(); // 2 2️⃣ Promises & Async/Await Promises handle async operations; async/await makes them read like sync code. Essential for APIs, timers, and non-blocking I/O. // Promise chain fetch(url).then(res => res.json()).then(data => console.log(data)).catch(err => console.error(err)); // Async/Await (cleaner) async function getData() { try { const res = await fetch(url); const data = await res.json(); console.log(data); } catch (err) { console.error(err); } } 3️⃣ Hoisting Declarations (var, function) are moved to the top of their scope during compilation, but initializations stay put. let/const are block-hoisted but in a "temporal dead zone." console.log(x); // undefined (hoisted, but not initialized) var x = 5; console.log(y); // ReferenceError (temporal dead zone) let y = 10; 4️⃣ The Event Loop JS is single-threaded; the event loop processes the call stack, then microtasks (Promises), then macrotasks (setTimeout). Explains why async code doesn't block. 5️⃣ this Keyword Dynamic binding: refers to the object calling the method. Changes with call site, new, or explicit binding. const obj = { name: "Sam", greet() { console.log(`Hi, I'm ${this.name}`); }, }; obj.greet(); // "Hi, I'm Sam" // In arrow function, this is lexical const arrowGreet = () => console.log(this.name); // undefined in global 6️⃣ Spread & Rest Operators Spread (...) expands iterables; rest collects arguments into arrays. const nums = [1, 2, 3]; const more = [...nums, 4]; // [1, 2, 3, 4] function sum(...args) { return args.reduce((a, b) => a + b, 0); } sum(1, 2, 3); // 6 7️⃣ Destructuring Extract values from arrays/objects into variables. const person = { name: "John", age: 30 }; const { name, age } = person; // name = "John", age = 30 const arr = [1, 2, 3]; const [first, second] = arr; // first = 1, second = 2 8️⃣ Call, Apply, Bind Explicitly set 'this' context. Call/apply invoke immediately; bind returns a new function. function greet() { console.log(`Hi, I'm ${this.name}`); } greet.call({ name: "Tom" }); // "Hi, I'm Tom" const boundGreet = greet.bind({ name: "Alice" }); boundGreet(); // "Hi, I'm Alice" 9️⃣ 💡 Practice these in a Node.js REPL or browser console to see how they interact. 💬 Tap ❤️ if you're learning something new!

🔑 JavaScript Set Reference – Quick Guide 1. Creation js const mySet = new Set(); // empty const letters = new Set(["a","b","c"]); // from array 2. Core Methods MethodPurposeExampleReturnsadd(value)Add elementmySet.add("x")Updated Setdelete(value)Remove elementmySet.delete("a")Booleanclear()Remove all elementsmySet.clear()Empty Sethas(value)Check existencemySet.has("b")true/falsesizeCount elementsmySet.sizeNumber 3. Iteration Methods MethodPurposeExampleforEach(callback)Run function for each valuemySet.forEach(v => console.log(v))values()Iterator of valuesfor (const v of mySet.values()) {}keys()Same as values()mySet.keys()entries()Iterator of [value, value] pairsmySet.entries() 4. Set Logic Methods (ES2025+) MethodPurposeunion(otherSet)Combine elements of both setsintersection(otherSet)Common elementsdifference(otherSet)Elements in one set but not the othersymmetricDifference(otherSet)Elements in either set but not bothisSubsetOf(otherSet)True if all elements are in other setisSupersetOf(otherSet)True if contains all elements of other setisDisjointFrom(otherSet)True if no common elements 5. Example Usage js const a = new Set([1,2,3]); const b = new Set([3,4,5]); console.log(a.union(b)); // {1,2,3,4,5} console.log(a.intersection(b)); // {3} console.log(a.difference(b)); // {1,2} console.log(a.symmetricDifference(b));// {1,2,4,5} 6. Key Notes Unique values only → duplicates ignored. Insertion order preserved. Sets are iterable (unlike WeakSets). Useful for mathematical set operations and fast membership checks. 🎯 Memory Hook Think of a Set as a mathematical set in code: No duplicates. Easy union/intersection/difference. Fast membership checks with .has().

⏱️ 𝗧𝗲𝘀𝘁𝗶𝗻𝗴 𝗔𝘀𝘆𝗻𝗰𝗵𝗿𝗼𝗻𝗼𝘂𝘀 𝗖𝗼𝗱𝗲 𝗶𝗻 𝗝𝗮𝘃𝗮𝗦𝗰𝗿𝗶𝗽𝘁 Async testing in JavaScript is one of those areas where things look correct — but fail silently if done wrong. 📞 🔙 𝗖𝗮𝗹𝗹𝗯𝗮𝗰𝗸-𝗕𝗮𝘀𝗲𝗱 𝗧𝗲𝘀𝘁𝗶𝗻𝗴 When your function depends on callbacks, your test must explicitly tell the test runner when it's done. it("should fetch data (callback)", (done) => {  fetchData((err, data) => {  if (err) return done(err);  expect(data).toBe("hello");  done(); // critical!  }); }); ❯❯❯❯ If you see callbacks → use done carefully. ⏳ 𝗣𝗿𝗼𝗺𝗶𝘀𝗲-𝗕𝗮𝘀𝗲𝗱 𝗧𝗲𝘀𝘁𝗶𝗻𝗴 Cleaner than callbacks, but still easy to mess up. You must return the promise from your test. it("should fetch data (promise)", () => {  return expect(fetchData()).resolves.toBe("hello"); }); ❯❯❯❯ Always return the promise OR use .resolves/.rejects. 🔄 𝗔𝘀𝘆𝗻𝗰/𝗔𝘄𝗮𝗶𝘁 𝗧𝗲𝘀𝘁𝗶𝗻𝗴 (𝗠𝗼𝗱𝗲𝗿𝗻 𝗦𝘁𝗮𝗻𝗱𝗮𝗿𝗱) The cleanest and most readable approach. it("should fetch data (async/await)", async () => {  const data = await fetchData();  expect(data).toBe("hello"); }); Handling errors - it("should throw error", async () => {  await expect(fetchData()).rejects.toThrow("error"); }); ❯❯❯❯ If you use async, always use await where needed. ✍ 𝗞𝗲𝘆 𝗧𝗮𝗸𝗲𝗮𝘄𝗮𝘆𝘀 ♦️ Callbacks → use done() ♦️ Promises → return the promise ♦️ Async/Await → use await properly ♦️ Always test both success AND failure paths. 👉 We’ll dive deeper into 𝗕𝗲𝘀𝘁 𝗣𝗿𝗮𝗰𝘁𝗶𝘀𝗲𝘀 𝗼𝗳 𝗧𝗲𝘀𝘁𝗶𝗻𝗴 in the upcoming posts. Stay tuned!! 🔔 Follow Nitin Kumar for daily valuable insights on LLD, HLD, Distributed Systems and AI. ♻️ Repost to help others in your network. #javascript #nodejs #testing #tdd #mocha #sinon #async

🪄 The Magic of Dependency Injection (DI) in Angular 🔹 What is Dependency Injection (DI)? 👉 Dependency Injection is a design pattern where Angular provides required dependencies instead of you creating them manually. 💻 Example constructor(private service: DataService) {} 💡 Angular automatically creates and injects the service for you. 🤔 Why DI is important? 1. Promotes loose coupling 2. Improves testability 3. Makes code scalable & maintainable Most Angular developers use DI… But very few actually master it 😮 The real power lies in Resolution Modifiers 👇 ✅ @Optional() 👉 “Give me the dependency… but don’t break if it’s missing” 💻 Example constructor(@Optional() private logger: LoggerService) {} ngOnInit() {  this.logger?.log('Component Loaded'); } 🧠 Use Case 1. Feature-based logging 2. Optional services (like analytics, plugins) 👉 If LoggerService is not provided → app won’t crash 💡 @Self() 👉 “Only look in my component” 💻 Example constructor(@Self() private service: LocalService) {} 🧠 Use Case 1. When you want component-specific service instance 2. Avoid accidentally using global/shared service 👉 Useful in form controls / reusable components ⏭ @SkipSelf() 👉 “Ignore me, go to parent” 💻 Example constructor(@SkipSelf() private parentService: DataService) {} 🧠 Use Case 1. When child overrides a service but still needs parent version 2. Prevent circular or duplicate injections 👉 Common in nested components / shared state 🏠 @Host() 👉 “Stop at host component” 💻 Example constructor(@Host() private control: ControlContainer) {} 🧠 Use Case 1. Angular Forms (very common 🔥) 2. Ensure dependency comes from host component only 👉 Used in: FormGroupDirective, Custom form controls ⚡ Senior-Level Insight 👉 Angular DI is not just injection 👉 It’s a hierarchical tree traversal system Angular DI is basically: 👉 Tree traversal + resolution rules 🧠 One-line Summary @Optional() → Safe injection @Self() → Only current level @SkipSelf() → Skip current, use parent @Host() → Restrict to host 🚀 Real-world scenario (combined) 1. Global AuthService (App level) 2. Feature-level override 3. Component-specific config 👉 These modifiers help you control which version gets injected 💬 Ever debugged a DI issue that took hours? 😅 Drop it below — let’s discuss! #Angular #DependencyInjection #Frontend #WebDevelopment #JavaScript #RxJS #AngularDeveloper #TechTips

Your scraper worked fine yesterday. Today it returns empty results. Nothing changed on your end. But the data is gone. This is the classic Ajax crawling problem, and it hits almost every developer who builds their own scraper. Here's what's actually happening 👇 • 99% of websites now load content dynamically via JavaScript • Traditional crawlers only fetch static HTML and miss the dynamic part entirely • Empty fields, broken pagination, missing lazy-loaded data are all symptoms of the same root cause • Python-based fixes (Selenium, Playwright) work short-term, but maintenance costs 10x the initial build The modern web wasn't built for traditional crawlers. Your tooling needs to catch up. Read the full breakdown, including three core Ajax crawling methods and a no-code alternative: https://lnkd.in/gdny4kJv #WebScraping #DataExtraction #NoCode #Automation #Python

🚀 JavaScript Simplified Series — Day 34 Objects are powerful… But what if you could **share properties and methods between objects automatically?** 🤔 Without copying code again and again 😵 This is where **Prototypes** come in 🔥 --- ## 🔥 The Problem ```javascript id="pt1" let user1 = { name: "Abhay", greet: function() { console.log("Hello") } } let user2 = { name: "Rahul", greet: function() { console.log("Hello") } } ``` 👉 Same function repeated ❌ 👉 Code duplication ❌ --- ## 🔥 Solution → Prototype JavaScript objects have a hidden property: 👉 **[[Prototype]]** Through this, objects can **inherit properties** --- ## 🔹 Example ```javascript id="pt2" function User(name) { this.name = name } User.prototype.greet = function() { console.log("Hello " + this.name) } let u1 = new User("Abhay") let u2 = new User("Rahul") u1.greet() u2.greet() ``` 👉 Output: Hello Abhay Hello Rahul --- ## 🔍 What’s happening? 👉 `greet()` is not inside object 👉 It is shared via prototype 📌 Memory efficient + reusable --- ## 🔥 Real Life Example Think of a **template 🧾** 👉 Same format 👉 Different data Like: Form template → reused for all users --- ## 🔥 Prototype Chain If property not found: 👉 Object → Prototype → Next Prototype → null --- ## 🔥 Simple Summary Prototype → shared properties Avoid duplication Enable inheritance --- ### 💡 Programming Rule **Don’t repeat logic. Share it using prototypes.** --- If you want to learn JavaScript in a **simple and practical way**, you can follow these YouTube channels: • Rohit Negi • Hitesh Choudhary Choudhary (Chai aur Code) --- 📌 Series Progress Day 1 → What is JavaScript Day 2 → Variables & Data Types Day 3 → Type Conversion & Operators Day 4 → Truthy & Falsy + Comparison Operators Day 5 → If Else + Switch + Ternary Day 6 → Loops Day 7 → Break + Continue + Nested Loops Day 8 → Functions Basics Day 9 → Arrow + Default + Rest Parameters Day 10 → Callback & Higher Order Functions Day 11 → Arrays Basics Day 12 → Array Methods Day 13 → Array Iteration Day 14 → Advanced Array Methods Day 15 → Objects Basics Day 16 → Object Methods + this Day 17 → Object Destructuring Day 18 → Spread & Rest Day 19 → Advanced Objects Day 20 → DOM Introduction Day 21 → DOM Selectors Day 22 → DOM Manipulation Day 23 → Events Day 24 → Event Bubbling Day 25 → Event Delegation Day 26 → Async JavaScript Day 27 → Promises Day 28 → Async / Await Day 29 → Fetch API Day 30 → Event Loop Day 31 → Scope Day 32 → Hoisting Day 33 → Closures Day 34 → Prototypes Day 35 → Classes (Next Post) --- Follow for more 🚀 #JavaScriptSimplified #javascript #webdevelopment #coding #programming #learninpublic #100DaysOfCode #frontenddevelopment #devcommunity #codingjourney #softwaredeveloper #techcommunity #dailylearning #codeeveryday

Day 1/100 of Javascript Today Topic : Javascript Engine JS code is first tokenized and parsed into an AST (Abstract Syntax Tree). The interpreter converts this into bytecode and begins execution. While running, the engine identifies hot code and uses a JIT compiler to optimize it into machine code for better performance. 1. What is Tokenizing? Tokenizing = breaking your code into small meaningful pieces (tokens) After tokenizing: Code Part Token Type let keyword x identifier = operator 10 literal ; punctuation 2. What Happens After Tokenizing? Tokens → Parsing Parser converts tokens into: 👉 AST (Abstract Syntax Tree) Example (conceptually): VariableDeclaration ├── Identifier: x └── Literal: 10 3. Why JavaScript is JIT Compiled? JS is called JIT (Just-In-Time) compiled because: 👉 It compiles code during execution, not before. ⚙️ Flow Code → Tokens → AST → Bytecode → Execution → Optimization → Machine Code 🔥 Step-by-Step 1. Interpreter Phase AST → Bytecode Starts execution immediately 👉 Fast start, but not the fastest execution 2. Profiling Engine watches: Which code runs frequently (hot code) 3. JIT Compilation Hot code → compiled into optimized machine code 👉 Now it runs much faster Also looked at different JavaScript engines: 👉V8 (Google) → Uses Ignition (interpreter) + TurboFan (optimizer), heavily optimized for performance 👉SpiderMonkey (Mozilla) → Uses Interpreter + Baseline + IonMonkey (JIT tiers) 👉Chakra (Microsoft) → Has its own JIT pipeline with profiling and optimization stages Each engine has a different internal architecture, but all follow the same core idea. Reference : 1. https://lnkd.in/gvCjZRJK 2. https://lnkd.in/gwcWp-dE 3. https://lnkd.in/gWGiNJZk. 4. https://lnkd.in/g7D4MiQ8 #Day1 #JavaScript #100DaysOfCode