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Building a Lightweight Product Filter with Vanilla JavaScript While building a small e-commerce project, I wanted users to filter products instantly without refreshing the page. Instead of relying on a frontend framework, I opted for a simple solution using HTML data attributes, vanilla JavaScript, and a little CSS. The goal was straightforward: let visitors filter items by size while keeping the interface fast, responsive, and easy to maintain. HTML Structure Each product card stores its information in data-* attributes. This keeps the markup clean and makes filtering straightforward. <div class= "filters" > <button class= "filter-btn" data-filter= "all" > All </button> <button class= "filter-btn" data-filter= "small" > S </button> <button class= "filter-btn" data-filter= "medium" > M </button> <button class= "filter-btn" data-filter= "large" > L </button> </div> <div class= "product-grid" > <div class= "product-card" data-size= "medium" data-style= "cargo" > Cargo Shorts </div> <div class= "product-card" data-size= "large" data-style= "chino" > Chino Shorts </div> <!-- More product cards --> </div> Using data attributes means you can add new filter categories later without changing your overall structure. JavaScript Filtering Logic The filtering logic listens for button clicks and simply shows or hides product cards based on the selected size. const filterButtons = document . querySelectorAll ( " .filter-btn " ); const productCards = document . querySelectorAll ( " .product-card " ); filterButtons . forEach (( button ) => { button . addEventListener ( " click " , () => { const filterValue = button . dataset . filter ; productCards . forEach (( card ) => { const cardSize = card . dataset . size ; if ( filterValue === " all " || cardSize === filterValue ) { card . classList . remove ( " hidden " ); } else { card . classList . add ( " hidden " ); } }); filterButtons . forEach (( btn ) => btn . classList . remove ( " active " )); button . classList . add ( " active "

Hi guys ! I'm a new developer who's interested in data science and artificial intelligence. To showcase what I learnt thus far, I've started writing articles, with my first one being published here ! One of the most difficult parts of getting into machine learning was the overload of terminology that tutorials had, even when explaining basic concepts such as how a neural network itself would function. Because of this, I've written an article (see above) that simplifies it while ensuring the main concepts are sufficiently explained; it requires no mathematical background and will only take less than 5 minutes to read ! I hope you find it informative and well written, and I highly welcome any suggestions or corrections that might be suggested to improve my future articles !

Series: Master OOP for Software Engineering Interviews Introduction Ask ten beginner developers: "What is abstraction?" Most answers sound like this: "Abstraction is the process of hiding implementation details and showing only essential information." Technically, that's correct. But if I ask the next question: "Why was abstraction invented?" or "Can you explain abstraction using an Inventory Management System?" or "How is abstraction different from encapsulation?" many candidates struggle. That's because they memorized the definition instead of understanding the idea behind it. In this article, we'll learn abstraction the way experienced software engineers think about it—not by memorizing definitions, but by understanding why it exists, what problem it solves, and how it appears in every modern software system. 🎯 Learning Goals After reading this article, you should be able to: Explain abstraction without memorizing a textbook definition. Understand why abstraction exists. Identify abstraction in everyday life. Recognize abstraction in software systems. Confidently answer beginner interview questions. Build a strong mental model that makes future OOP concepts easier. Before We Learn Abstraction... Let's ask an important question. Why do programming languages even provide OOP? Imagine writing software for an e-commerce company. The system contains: Products Customers Orders Warehouses Payments Delivery Partners Notifications Discounts Reviews Thousands of features. If every developer had to understand every implementation detail before writing code, software development would become impossible. We need a way to reduce complexity. That solution is called abstraction. The Problem Abstraction Solves Imagine buying a new car. You sit inside. You: Press the accelerator. Turn the steering wheel. Shift gears. Press the brake. Simple. But underneath the hood, hundreds of complex operations happen every second. The engine burns fuel. The pistons move. The gearbox changes tor

When I first heard the term backtracking , it sounded like a complicated algorithm reserved for computer scientists. After spending the last couple of weeks learning it and implementing it in a Tetris Optimizer project, I realized something surprising: Backtracking is simply the art of making a decision, checking whether it works, and if it doesn't, undoing it and trying something else. This article explains backtracking using a practical project instead of abstract examples. The Problem Imagine you have several Tetris pieces (tetrominoes), and your goal is to fit all of them into the smallest possible square . It might look something like this: A A A A B B B B C C C C D D D D The challenge is to arrange every piece so that: No pieces overlap. No piece extends outside the board. Every piece is used exactly once. The board is as small as possible. This is much harder than it looks. My First Thought Initially, I thought I could simply place one piece after another. Place A Place B Place C Place D Done! Unfortunately, programming isn't always that kind. Sometimes the first position you choose for piece A makes it impossible to place D later. The mistake wasn't with D . The mistake happened much earlier. Enter Backtracking Backtracking works like this: Place a piece. Try placing the next one. If you get stuck... Remove the last piece. Try a different position. Repeat until every piece fits. It's essentially saying: "If this path doesn't work, let's go back and explore another one." Visualizing the Search Suppose we have four tetrominoes. Start ├── Put A at (0,0) │ ├── Put B │ │ ├── Put C │ │ │ ├── D fits ✅ │ │ │ └── D fails ❌ │ │ └── Try another position │ └── Move A elsewhere └── Try another position for A Every branch represents another possibility. Backtracking explores these branches until it finds one that works. How It Looks in Go The heart of the algorithm is surprisingly small. func solve ( index int ) bool { if index == len ( pieces ) { return true } for every

A product idea from RayTally's daily scan of public signals. The idea One-liner: Helps first-time PCB designers find manufacturing and assembly problems on the board before they place an order. Concept: A desktop preflight tool helps first-time PCB designers find contradictions among their manufacturing files before payment. Users drag in Gerber files, a bill of materials, and placement coordinates. The first screen highlights high-risk locations such as board outlines, hole sizes, package orientation, and missing components. Clicking an issue locates the specific pad on the board and shows the design value beside the fabricator's rule. The tool also simulates panelization and the board's appearance after component placement, exposing problems such as insufficient connector overhang and component collisions before they happen. It does not require beginners to read an entire manufacturing standard; it focuses each check on the changes needed for the current order. Why now On July 11, 2026, a first-time board designer publicly documented the full process from designing in KiCad and exporting Gerber and drill files with default settings to sending them to a fabricator and assembling the board by hand. Before powering it on, he still put the odds of a first successful result at "fifty-fifty." At the July 13, 2026, 09:46 UTC capture, the experience had an observed score of 111 and 45 comments on Hacker News. KiCad already provides baseline capabilities including DRC, Gerber viewing, 3D viewing, and manufacturing-file output. Consolidating these scattered steps into one order-level preflight directly addresses the question beginners face before payment: what exactly should they check? Signal Hacker News "Designing and assembling my first PCB" (approximately 111 points and 45 comments, observed July 13, 2026, 09:46 UTC). RayTally scans public signals daily for product ideas worth building. Browse the source page and more product ideas .

7 MongoDB Query Mistakes That Return the Wrong Results VisuaLeaf VisuaLeaf VisuaLeaf Follow Jul 14 7 MongoDB Query Mistakes That Return the Wrong Results # mongodb # coding # software # database 3 reactions Add Comment 5 min read

Hi everyone! I'm a tech enthusiast currently mastering web development and game development. I am building my foundation from scratch,learning on my phone with Sololearn and Mimo while writing my code completely on a tablet using an app called Acode . Why I'm Doing This I want to learn how to turn big ideas into reality, one line of code at a time. I'm starting with the absolute basics of the web: HTML. My First HTML Project Today, I built a multi-page setup right on my tablet. Here is the structure of my homepage ( index.html ): <!DOCTYPE html> <html lang= "en" > <head> <title> My First Blog Post </title> </head> <body> <h1> Day 1: Starting My Journey To Become A Web Developer </h1> <p> I officially started learning web development today! </p><h3> What I Learnt </h3><Some of the things I learnt today were: </ p ><ul><li> HTML code controls the structure of a webpage </li><li> HTML tags are used to add elements to a webpage </li><li> Elements like button and paragraph require container tags while elements like images and line break only require empty tags <li> Container tags consist of both opening and closing tags. </li><li> Some HTML tags known as Semantic tags </li></ul><h4> What I Built </h4><p> I started with my first project which is my portfolio website </p><h5> Looking Ahead </h5><p> Next I want to learn more on HTML and dive deeper to get a better understanding of HTML and later learn CSS and JavaScript to style and make my webpage more interactive <p> </body> </html> ``` What's Next? ​My next immediate goal is to learn more about HTML and to learn CSS so I can start styling these pages and making them look awesome. After that, I'll be diving into JavaScript and starting my first simple game development projects. ​I'm excited to document my progress here as I grow from a beginner into a software developer. If you have any tips for learning on a mobile device, let me know in the comments!

In indie game development, one of the biggest challenges is finding high-quality assets to bring our ideas to life. My goal has always been to create a complete world that stands out from the asset-saturated market, which often feels repetitive and even boring. However, I noticed that most available resources are low-resolution, typically 16x16. While 16x16 sprites have been functional for years, modern game engines allow for much greater detail while still preserving that classic retro vibe. The typical workaround has been to simply scale 16x16 sprites twice to make them 32x32, or three times for 48x48. This approach sacrifices an incredible amount of potential detail just to optimize... I'm not even sure what, since the file sizes end up being practically the same. That is why choosing a 48x48 pixel grid was not a random decision. In modern pixel art, this size represents the perfect balance between the classic nostalgia of 16-bit systems and the need for contemporary expressiveness. Plus, when I first started creating graphics, I was primarily using RPG Maker MV (RMMV), which has a native 48x48 grid. With a lower resolution, I would have lost the ability to subtly animate a character's gaze, individual movements, or the flow of their hair. Minor details—like wall sketches or windows with lighting that shifts depending on the time of day—would have been impossible. On the other hand, transitioning to other game engines made me realize two critical points about shifting to an even higher resolution. First, and most basic, is the workload: a larger canvas means significantly more work (which is why it’s easier to draw in 16x16 and let the software upscale it). Second, going too high causes the art to lose that retro charm I wanted to preserve at all costs as a core part of my brand. When I started designing this universe, I initially thought of a cozy, soft, pastel color palette. However, those styles tend to feel too modern and lacked that genuine retro feel. So, I

Hey what's up guys👋🏻 Remember our last Perfect Circle challenge? We had some amazing attempts! While...

TL;DR A "loop" is not an agent grading its own work. It is an external script that re-runs the agent, plus a separate check the agent cannot edit. I turned "feels smooth" into an FPS number and let the loop optimize toward it. I set the target too high to be reachable on a 60Hz screen. The loop kept failing but never faked the result. The bug was in my number, not the code. Could I get an AI agent to make my website faster without me sitting there, running it, reading the numbers, and running it again? That is what this series is about. Not how I built a website, because the website is boring on purpose, but how you wrap an agent in a loop that works toward a goal on its own, and how you stop it from cheating along the way. In this first part I want to explain what a loop actually is, because there is a common misconception, and then walk through a real one. I set this loop a target that was physically impossible to reach and watched what it did. That run taught me more than a passing test would have. This is Part 1 of 3. All three parts use the same small movie-poster website as the example, but the website is never the point. What a loop is, and what it is not I had a wrong idea about this at first, so let me clear it up. A loop is not an agent prompting itself, grading its own work, and deciding when it is done. An agent left to mark its own homework will usually tell you it passed. A loop is closer to this: an external script runs the agent, a separate check that the agent cannot edit decides whether the result is good, and that repeats until the check passes or you hit a limit. There are three parts to it that come up again and again: The driver: the script that re-runs the agent. This is the thing that removes the manual work, not the agent. The gate: the check that decides pass or fail. The agent makes changes, but it never decides when to stop. The cap: a limit, so a stuck loop gives up instead of running forever. One rule matters more than the rest. The thi

On July 12, 2026 I asked a free API to guess the age of someone named Xzqwlptv. It answered in a few milliseconds: HTTP 200, valid JSON. # runnable, read-only: no key needed curl -s "https://api.agify.io?name=Xzqwlptv" {"count":0,"name":"Xzqwlptv","age":null} # HTTP 200 OK Status 200. The JSON parses. The age key is present, exactly where a schema says it belongs. Its value is null . Every guard I usually reach for passes this response: if resp.ok , if "age" in data , even a JSON Schema that requires an age property. The null walks straight past all of them and into the dataset. My earlier keyless-API posts kept circling one idea from different angles. HTTP 200 does not mean the read worked, because the body can be empty. HTTP 201 Created does not mean a write happened, because the read-back returns 404. This post moves the lie one level deeper than either of those. Here the status is 200, the body arrives, it parses, it matches your schema, and the field you came for is sitting right there. The value is just empty. The null that passes your schema check. A free fun or facts API here means a public endpoint that returns a joke, a fact, or a guess about a name, with no API key, no signup, and no credit card. A URL you can paste into a terminal right now. Ten of them clear that bar, and I re-verified every response below with a live curl on July 12, 2026: real HTTP code, real body, trimmed but never reworded. One scope note first, so the numbers stay honest. I curl-verified all ten APIs on July 12, 2026. I have not run any of them in production. My 2,190 production scraper runs (962 of them on a single Trustpilot scraper) are a different domain, and I cite them for one reason only: they are why I read a field's value and its confidence instead of its status line. That number is not a claim about these ten endpoints. # API What it returns Example call The empty success to watch 1 agify.io Age guess from a first name GET api.agify.io?name=Xzqwlptv 200 with age: null 2 g

In the previous article , we learned that an Origin consists of three components: Scheme (Protocol) Host Port Browsers use these three components to determine whether a request is Same-Origin or Cross-Origin . Whenever a web page attempts to access resources from a different Origin, a security mechanism called CORS (Cross-Origin Resource Sharing) comes into play. 📌 Why Does a CORS Error Occur? Suppose your web application is running at: https://app.example.com Now it tries to fetch data from: https://api.example.com Although both URLs belong to example.com , their Hosts are different. That means they have different Origins. As a result, the browser treats this as a Cross-Origin request. If the destination server does not explicitly allow this Origin, the browser prevents JavaScript from accessing the response, resulting in what we commonly call a CORS Error . 💡 Important: CORS is a browser security mechanism , not a server security mechanism. ⚠️ A Common Misconception About CORS Many developers believe that a CORS error means the request never reached the server. In most cases, that's simply not true. Typically: ✅ The browser sends the request. ✅ The server receives it. ✅ The server generates and returns a response. ❌ The browser blocks JavaScript from accessing that response. In other words, the request was successful—the browser simply refuses to expose the response to your application because the CORS policy was not satisfied. This is why sending the exact same request using tools like Postman or curl usually works without any problems. Those tools are not browsers, so they do not enforce browser security policies like CORS. 📦 How Does the Server Handle CORS? To allow JavaScript to access the response, the server must include the appropriate CORS headers. The most important one is: Access-Control-Allow-Origin: https://app.example.com This header tells the browser that JavaScript running on https://app.example.com is allowed to read the response. ✅ Examples Suppos

Module caching, execution order, and circular imports explained by tracing what actually happens. How Python's Import System Works and Why It Matters for Debugging The import system is one of the least understood parts of Python and one of the most practically important for debugging production issues. Circular import errors, unexpected code execution, and module state bugs all stem from not understanding what happens when Python encounters an import statement. What Happens on the First Import When Python executes import mymodule for the first time: Python checks sys.modules for mymodule . If found, returns the cached module object immediately. If not found, Python locates the module file. Python creates a new module object and adds it to sys.modules under the module name. Python executes the module file's code in the new module's namespace. The name mymodule in the importing module is bound to the module object. Step 3 happens before step 4. This is critical for understanding circular imports. The Module Cache import sys import os print ( " os " in sys . modules ) print ( sys . modules [ " os " ] is os ) Output: True True Every imported module is cached in sys.modules . Subsequent imports return the cached object without re-executing the module code. Module-Level Code Executes on Import # config.py print ( " config module loading " ) DEBUG = True print ( f " DEBUG is { DEBUG } " ) # main.py import config import config # second import print ( config . DEBUG ) Output: config module loading DEBUG is True True The print statements in config.py run exactly once — when the module is first imported. The second import returns the cached module object without re-executing the code. Circular Import Behavior # module_a.py print ( " loading module_a " ) from module_b import b_function def a_function (): return " from a " # module_b.py print ( " loading module_b " ) from module_a import a_function def b_function (): return " from b " When you import module_a , Python starts exe

We're surrounded by data every single day. Every online purchase, website visit, customer review, or...

Hello, I'm Maneshwar. I'm building git-lrc, a Micro AI code reviewer that runs on every commit. It is...

Introdução Validar dados é uma responsabilidade que pode ficar na aplicação, no banco de dados, ou em ambos. Deixar tudo na aplicação é arriscado: diferentes sistemas podem acessar o mesmo banco, migrações podem rodar diretamente, um bug pode deixar passar um valor inválido. Constraints são regras definidas no próprio banco de dados — uma camada de proteção que age independente de quem está escrevendo os dados. PRIMARY KEY A chave primária identifica cada linha de forma única. Ela combina duas restrições implicitamente: NOT NULL e UNIQUE . Nenhuma linha pode ter o mesmo valor de chave primária, e nenhuma pode tê-la nula. CREATE TABLE clientes ( id INT PRIMARY KEY , nome VARCHAR ( 100 ) NOT NULL ); Quando a chave primária envolve mais de uma coluna, ela é declarada separadamente: CREATE TABLE matriculas ( aluno_id INT , curso_id INT , PRIMARY KEY ( aluno_id , curso_id ) ); Na maioria dos bancos, é comum usar uma chave primária auto-incremental para não precisar gerenciar os IDs manualmente: -- PostgreSQL id SERIAL PRIMARY KEY -- MySQL id INT AUTO_INCREMENTPRIMARY KEY -- SQL padrão (suportado por ambos) id INT GENERATED ALWAYS AS IDENTITY PRIMARY KEY FOREIGN KEY A chave estrangeira garante integridade referencial : um valor só pode existir numa coluna se ele existir como chave primária na tabela referenciada. É o que torna os relacionamentos entre tabelas confiáveis. CREATE TABLE pedidos ( id INT PRIMARY KEY , cliente_idINT REFERENCES clientes ( id ) ); Tentar inserir um pedido com cliente_id = 99 quando não existe cliente com esse id resulta em erro imediato. O banco rejeita a operação antes mesmo de ela chegar ao disco. O comportamento quando o registro referenciado é deletado pode ser configurado: CREATE TABLE pedidos ( id INT PRIMARY KEY , cliente_id INT REFERENCES clientes ( id ) ON DELETE CASCADE -- deleta os pedidos junto com o cliente ON UPDATE CASCADE -- atualiza o cliente_id se o id do cliente mudar ); As opções disponíveis são: Opção Comportamento RESTRICT

Introdução Consultas individuais respondem perguntas como "qual o email do cliente 42?". Mas as perguntas mais valiosas em qualquer sistema são de outro tipo: "qual o produto mais vendido?", "qual a receita média por pedido?", "quantos clientes se cadastraram esse mês?". Para responder isso, o SQL oferece as funções de agregação — operações que recebem um conjunto de linhas e devolvem um único valor resumido. Para os exemplos a seguir, considere esta tabela: pedidos: | id | cliente | produto | categoria | quantidade | valor | |----|------------|-------------|--------------|------------|--------| | 1 | Ana Lima | Notebook | Eletrônicos | 1 | 3500.00| | 2 | Ana Lima | Mouse | Periféricos | 2 | 80.00| | 3 | Bruno Melo | Teclado | Periféricos | 1 | 150.00| | 4 | Bruno Melo | Notebook | Eletrônicos | 1 | 3500.00| | 5 | Carla Nunes| Monitor | Eletrônicos | 2 | 1200.00| | 6 | Carla Nunes| Mouse | Periféricos | 1 | 80.00| As Funções de Agregação COUNT Conta o número de linhas — ou de valores não nulos em uma coluna específica. -- Total de pedidos SELECT COUNT ( * ) AS total_pedidosFROM pedidos ; -- Resultado: 6 -- Clientes distintos que fizeram pedidos SELECT COUNT ( DISTINCT cliente ) AS clientes_unicosFROM pedidos ; -- Resultado: 3 COUNT(*) conta todas as linhas, incluindo as que têm nulos. COUNT(coluna) conta apenas as linhas onde aquela coluna não é nula. COUNT(DISTINCT coluna) conta valores únicos — útil para saber quantos clientes, produtos ou categorias distintos aparecem no resultado. SUM Soma os valores de uma coluna numérica. -- Receita total SELECT SUM ( valor ) AS receita_total FROM pedidos ; -- Resultado: 8510.00 -- Total de itens vendidos SELECT SUM ( quantidade ) AS itens_vendidos FROM pedidos ; -- Resultado: 8 AVG Calcula a média aritmética dos valores. -- Valor médio por pedido SELECT AVG ( valor ) AS ticket_medio FROM pedidos ; -- Resultado: 1418.33 AVG ignora valores nulos automaticamente — calcula a média apenas sobre os registros que têm valor preenchid

Generally, when a user asks a query, the system searches for the relevant chunks stored in the vector database using cosine similarity. The better we can filter the data, the smaller the search space becomes, resulting in faster and more efficient retrieval. Suppose we have a book with 10 chapters. If we want to search for a particular topic, all the points in the vector database are compared with the user query, and only the closest points are retrieved. This process is called KNN (K-Nearest Neighbors) . Another algorithm is ANN (Approximate Nearest Neighbors) . Instead of checking all the points in the vector database, ANN searches only within a smaller region based on the proximity of the data. As the name suggests, it does not always return the exact result, but it provides the most preferred or approximate results much faster. Is there any other method we can use to make the search more effective? Metadata Filtering Metadata means data about the data . Metadata is stored along with each chunk. It can contain information related to the chunk, such as the chapter name, topic description, author, or any other relevant details. When the user query contains information related to the metadata (for example, a chapter name or topic), the system can directly filter the relevant chunks before performing vector similarity search. This technique is called metadata filtering . Metadata filtering is supported by: Pinecone ChromaDB Qdrant FAISS does not provide built-in support for metadata filtering. Reranking Documents are first split into chunks, and each chunk is converted into vectors and stored in the vector database. When a user query arrives, it is converted into a vector and searched against the vector database to retrieve the closest chunks. However, we do not know whether the retrieved documents are actually the most relevant to the query. It is not always true that the closest vectors represent the most relevant documents. How Reranking Works The documents retrie

For 4 years, I lived in the world of IT Operations. My days were spent handling incident response, managing data lifecycles, and making sure systems stayed online. I learned how to troubleshoot under pressure, talk to frustrated users, and keep the business running. But I had a lingering frustration: I was always fixing other people's code. I never got to build it. And more importantly, I was fixing problems manually that I knew could be automated. So, I decided to make a massive pivot. I went back to university (VILNIUS TECH) and recently started a Java Engineering internship at Coherent Solutions. My goal isn't just to become a Java developer. My goal is to bridge the gap between Development and Operations- DevOps . In my first few weeks at Coherent, we started learning about enterprise architecture. But the moment that truly clicked for me was when I built my first Docker image for our project. In my past IT life, deploying an app was a nightmare. "It works on my machine!" was a constant joke (and a constant headache for the Ops team). Setting up environments, installing the right Java version, configuring databases—it was manual, error-prone, and boring. Then I wrote a Dockerfile . I packaged our Java application and its dependencies into a single, isolated container. Suddenly, I realized: This is how you solve the "works on my machine" problem forever. As someone who used to be the guy manually fixing those environment issues, writing a few lines of code to completely automate that process felt like a superpower. I'm starting this blog to document my journey in real-time. I'm currently diving deep into: 🔹 Java 21 (the newest LTS—highly recommend checking out Virtual Threads!) 🔹 Spring Boot & enterprise backend architecture 🔹 Docker & containerization 🔹 Next up: CI/CD pipelines and Infrastructure as Code (Terraform) If you are currently stuck in IT Support or SysAdmin roles and dreaming of becoming a DevOps or Software Engineer—you aren't alone. Let's learn toge

Hello, I'm Maneshwar. I'm building git-lrc, a Micro AI code reviewer that runs on every commit. It is...