Implementing expect() Function for JavaScript Testing

🚀 Day 4 of My 30 Days of JavaScript Journey ✅ Challenge: Create Counter Object (LeetCode #2665) Write a function createCounter(init) that returns an object with three functions: increment() → increases the value by 1 and returns it. decrement() → decreases the value by 1 and returns it. reset() → resets the value to the initial value and returns it. 💻 Language Used: JavaScript ❓ Problem Link: https://lnkd.in/gKxPxb8Y 💡 Solution: https://lnkd.in/g3jv6Nfi 🧠 Concept Highlighted: This challenge strengthens understanding of closures and object methods in JavaScript. It shows how functions can preserve and modify internal state — a key concept in building dynamic, stateful applications. #JavaScript #LeetCode #30DaysOfCode #CodingChallenge #WebDevelopment #FrontendDevelopment #LearningEveryday #Closures #ProblemSolving

🚀 Day 4 of My 30 Days of JavaScript Challenge 🧩 Problem: Create Counter II (LeetCode #2665) Write a function createCounter(init) that returns an object with three functions: increment() → increases the current value by 1 and returns it decrement() → decreases the current value by 1 and returns it reset() → resets the value back to init and returns it 💻 Language: JavaScript ❓ Question: https://lnkd.in/eupkr-a3 💡 Solution: https://lnkd.in/eq3BEsn2 🧠 Concepts Used: Closures for maintaining private state across function calls Object methods to encapsulate multiple related actions State management inside functions 📚 Takeaway: This challenge reinforces closures and encapsulation — two powerful ideas that make JavaScript functions behave like real objects with memory and behavior. #Day4 #JavaScript #30DaysOfCode #LeetCode #CodingChallenge #WebDevelopment #FrontendDevelopment #100DaysOfCode

🚀 Day 2 of My 30 Days of JavaScript Journey ✅ Challenge: Counter Function (LeetCode #2620) Create a function createCounter(n) that returns another function. Each time the returned function is called, it should return the current value of n and then increment it by 1 — producing outputs like (n, n+1, n+2, ...). 💻 Language Used: JavaScript ❓ Problem Link: https://lnkd.in/gczTUyQ4 💡 Solution: https://lnkd.in/g2VVnv8u 🧠 Concept Highlighted: This problem reinforces the concept of closures — how JavaScript functions can "remember" variables from their outer scope even after the outer function has finished executing. It’s a foundational concept for mastering state management and functional programming in JS. 📘 My Takeaway: A small problem, but a powerful reminder that closures are at the heart of JavaScript. Understanding how functions preserve state paves the way for writing more efficient and modular code. Step by step, the logic becomes clearer! 💪 #JavaScript #LeetCode #30DaysOfCode #CodingChallenge #WebDevelopment #FrontendDevelopment #LearningEveryday #Closures

🚀 Day 11 of My 30 Days of JavaScript Journey ✅ Challenge: Memoize (LeetCode #2623) The task was to create a memoize(fn) function that caches results so that repeated calls with the same inputs return instantly from cache — without re-executing the original function. This helps improve performance when dealing with expensive computations like fibonacci or factorial, and even simple operations like sum when called repeatedly. 💻 Language Used: JavaScript ❓ Problem Link: https://lnkd.in/gnHmbPih 💡 Solution: https://lnkd.in/gGJZjYY9 🧠 Concept Highlighted: Memoization is a powerful optimization technique that uses caching to avoid repeating calculations. It strengthens understanding of closures, function arguments handling, and performance-oriented JavaScript. #JavaScript #LeetCode #30DaysOfCode #CodingChallenge #WebDevelopment #FrontendDevelopment #Memoization #PerformanceOptimization #LearningEveryday #ProblemSolving

🚀 Day 5 of My 30 Days of JavaScript Challenge 🧩 Problem: Apply Transform Over Each Element in Array (LeetCode #2635) Given an integer array arr and a mapping function fn, return a new array such that: newArray[i] = fn(arr[i], i) Solve this without using the built-in Array.map() method. 💻 Language: JavaScript ❓ Question: https://lnkd.in/eq8qYfpb 💡 Solution: https://lnkd.in/eT5U2kBp 🧠 Concepts Used: Higher-order functions (passing functions as arguments) Loops and callback functions Core idea behind how .map() works internally 📚 Takeaway: By recreating the Array.map() method manually, I learned how callback execution and array transformations work under the hood — a must-know for mastering JavaScript fundamentals. #Day5 #JavaScript #30DaysOfCode #LeetCode #CodingChallenge #WebDevelopment #FrontendDevelopment #100DaysOfCode

🚀 Day 10 of My 30 Days of JavaScript Challenge 🧩 Problem: Allow One Function Call (LeetCode #2666) Given a function fn, return a new function that ensures fn can only be called once. The first call returns the actual result, and every subsequent call returns undefined. 💻 Language: JavaScript 📖 Problem Link: https://lnkd.in/epnrfahZ 💡 Solution: https://lnkd.in/eGQKWkEk 🧠 Concepts Used Closures to store state (whether function is already called) Function Wrapping Higher-Order Functions 📚 Takeaway This problem is a great example of how closures preserve state between function calls — an essential concept for: Memoization API rate-limiting Event listener control #Day10 #JavaScript #30DaysOfCode #LeetCode #WebDevelopment #CodingChallenge #Closures #FrontendDevelopment #100DaysOfCode

Day 5 of #30DaysOfJavaScript: Creating My Own Filter Function from Scratch! 🎯 Today, I tackled a great exercise that challenged me to build a custom filter function without using JavaScript’s built-in .filter() method. This involved iterating over an array and using a callback function to decide which elements to keep based on truthy values. Here’s a peek at the solution I wrote: Key takeaways from this challenge: Deepened my understanding of higher-order functions and callback usage. Learned how to evaluate truthy and false values in JavaScript more effectively. Gained appreciation for the power and convenience of built-in array methods by implementing one manually. This hands-on approach is helping me grasp fundamental JavaScript concepts in detail while preparing for real-world coding challenges. Excited to keep growing and solving more problems along the way! Let’s connect and share knowledge. #JavaScript #CodingChallenge #WebDevelopment #LeetCode #ArrayMethods #LearningByBuilding #DeveloperJourney

🚀 Day 9 of My 30 Days of JavaScript Journey ✅ Challenge: Arguments Length (LeetCode #2703) Write a function argumentsLength that returns the total number of arguments passed to it — no matter how many or what type! This challenge is a simple yet powerful way to understand rest parameters in JavaScript. 💻 Language Used: JavaScript ❓ Problem Link: https://lnkd.in/g8gK65Cp 💡 Solution: https://lnkd.in/gJQyNBaq 🧠 Concept Highlighted: This problem emphasizes the use of rest parameters (...args) to handle variable-length arguments, a handy feature for building flexible and reusable functions in JavaScript. #Day9 #JavaScript #LeetCode #30DaysOfCode #CodingChallenge #WebDevelopment #FrontendDevelopment #LearningEveryday #ProblemSolving #ES6

🚀 Day 1 of My 30 Days of JavaScript Challenge 🧩 Problem: Create Hello World Function (LeetCode #2667) Write a function createHelloWorld that returns a new function which always returns "Hello World", no matter what arguments are passed. 💻 Language: JavaScript ❓ Question: https://lnkd.in/eVgQ9W87 💡Solution:https://lnkd.in/ed7AXEYr 🧠 Concept Used: JavaScript closures and higher-order functions Demonstrates how a function can return another function 📚 Takeaway: A simple yet powerful reminder that understanding function behavior and scope is key in JavaScript. Every small step builds stronger fundamentals! #JavaScript #LeetCode #30DaysOfCode #CodingChallenge #WebDevelopment #FrontendDevelopment #100DaysOfCode